Behenein debuted in February 2010. As the Indian Premier League season began and threatened to draw viewers away, the producers revealed their intention to introduce several plot twists, such as the revelation of the kidnapper of Smriti's baby, in order to keep the audience interested. Due to relatively good ratings, the channel planned to broadcast a four-hour recap in April, and is considering extending the show to one-hour episodes.It was the top 5 TRP shows of 2010-2011. It gained its highest TRP 6.1 and Lowest 0.9
On the day of Purva Shastri's wedding, her parents room catches fire while they are inside and they die. Purva (Poornima in Tamil) and her sisters Smriti (Shruthi in Tamil), Akashi (Aarti in Tamil) and Anokhi (Aruna in Tamil) are heartbroken and therefore she decides to postpone her wedding. After this incident, their aunt, Neema Ben comes with her son to take care of them. In truth, she wants her brother's property all for herself and leave the sisters homeless. But in her brother's will, he says that the property will go to Neema after all the 4 sisters get married and sign the will. Smriti is already married to her college sweetheart, famous lawyer named Mihir Sanghvi (Mahesh in Tamil) and is pregnant with his child. The sisters conceal the fact that their parents are dead from Smriti and also pretend that Purva is now married, because they do not want to give Smriti a shock that could affect her pregnancy.
The sisters try their best to conceal the fact from Smriti, however their attempts go in vain as Smriti finds out everything during her Godh Baraai (Baby shower Ceremony) due to plan made by Neema ben. She gets an unpleasant shock and is taken to the hospital. Here she gives birth to a healthy baby boy without any problems. Smriti too is heartbroken but she consoles herself. Her child is named Prem. Just as Smriti starts to get over the shock, her in-laws conspire to send her out of the house as they never liked her, because her marriage with Mihir was against their will. They ill treat her and drive her insane by keeping Prem away from her and proving her to be an irresponsible mother. In the end, her evil mother-in-law, Kamini and sister-in-law Shalaka succeed and admit her to a mental hospital.
After Smriti's admittance to the mental hospital, there is no mother to look after Prem. Since Mihir is a busy man and cannot watch over his son all the time, Kamini and Shalaka suggest him to remarry. Mihir makes a tough choice and decides to remarry. Kamini brings a young physocology student named Mansi to the house. She is a polite girl and visits Smriti at the mental hospital. She suggests Smriti to go through some therapies to improve her mental condition. She also takes very good care of Prem. Charmed by Mansi's good manners and moral values, the families arrange for their marriage. Nevertheless, Purva finds out that Mansi and her family are actually after the Sanghvi family's property and have no intention to look after Prem. Therefore, Purva pretends to be Mansi on her wedding day by putting her wedding dress and a veil over her face after she, Akashi and Anokhi tie up the real Mansi. Under these circumstances, Purva gets married to Mihir, in order to take care of Prem. Just as all the wedding rituals are over, Mansi frees herself and goes to face Purva. Purva reveals Mansi's true intentions to the whole family and she and her mother are driven away from the Sanghvi house. Purva and Mihir accept each other and the Sanghvi family accepts her as their daughter-in-law. However, Shalaka dislikes Purva as she is Smriti's sister. Nevertheless, they patch up as Purva saves Shalaka from suicide after she had a hard day in college.
As the time progresses Purva and Mihir begin to develop close feelings for one another. Amar Patel, Purva's ex-fiance, becomes heartbroken upon realizing the circumstances and moves to another town. After some time, Smriti ends up dying in a bus accident, and Mihir and Purva take their relationship to a higher level. Anokhi stays at her father's mansion happily, but Neema Ben plots to ruin Anokhi's life. She hires Samir, Anoki's love interest whom she met at dancing classes, to seduce Anokhi and rape her, thus forcing him to marry her.
Samir takes Anokhi to a hotel and tries to rape her, but luckily Anokhi is saved as Purva comes to her rescue. Purva finds out everything earlier as she already suspected Samir from the start and investigates. Samir admits the truth and is gone for good, but he doesn't tell anyone that Neema Ben was the one who hired him. When that plan fails, Neema Ben crashes Akashi's wedding day to her love, a lawyer named Kshitij (Ritesh in Tamil) when she hires a goon named Shamar Das (Verabadhra in Tamil) whom Akashi hates a lot, to kidnap Akashi and marry her. Thus, giving Shamar to Akashi as a wedding present. Shamar marries akashi on gun point and warns her that if she refuse to marry her , he will splash acid on her face .After Akashi's forced "wedding" , Shamar takes photographs of the wedding and sends her home after threatening her. Purva finds Akashi crying on their doorstep, but she refuses to tell anybody what happened. Purva and Mihir get copies of the photos and get to know about Akashi's wedding with Shamar, which she hid from them. Kshitij also receives a copy of them and refuses to accept Akashi afterwards as he marries someone else.
To seek revenge, Akashi goes to Shamar's house to ruin his life, as she is his legal wife. Shamar's mother and sister who work as servants at the Sanghvi house, being the reason that Akashi knew Shamar in the first place, become very close to her, therefore she begins to enjoy living there. Whereas, Mihir and Purva eventually fall in love during their honeymoon. Just when they start to get intimate, Smriti's lookalike, Aastha(Asha in Tamil) enters their life with a guy named Karan. Meanwhile, Akashi compels Shamar to get a job and therefore, he gets a job as a Taxi driver. So, one day he takes Akashi on a ride and hits a tree. Here, Akashi gets injured and bleeds and is given a lot of care and affection by Shamar which finally makes things better between them.
Later it is revealed that Aastha is actually Smriti in disguise. Smriti gets married to Karan, since she thought that it was the only way to stop Purva from finding out the truth. Anokhi already finds out the truth before anybody else does, as she hears Aastha singing Prem's lullaby and confronts her about it. However, after listening to Smriti's pleas, Anokhi keeps this between them. Love blossoms between Akashi and Shamar as Shamar brings her an anklet out of his salary. They stop fighting for good and Smriti also starts enjoying her new life with Karan. Anokhi also finds a new love interest, Bhavesh (Bharat in Tamil) who is a friend of Karan and slowly starts to fall for him. Anokhi and Bhavesh met as Bhavesh phoned her in a wrong number. Meanwhile, Kshitij takes up the courage to go near Akashi to apologize her but Akashi rejects him. Here it is revealed that Kshitij cancels his wedding with the other girl, since he still loves Akashi and cannot replace her with anyone else. Akashi invites Shamar to her birthday party where they both enjoy teasing each other. A few days later, Akashi and Mihir have a fight with Mihir giving her two choices; the first being Shamar Das and the second being his mansion. However Akashi chooses to stay with Shamar causing more tension between the two. Anokhi's engagement ceremony is stopped as Bhavesh's sister Jigna has not arrived yet. They also find out that she came two days earlier in order to surprise Bhavesh.
Not finding her, they all are worried and start to wonder whether death encountered her leading to Purva and Mihir arguing with one another. Smriti is greatly upset as Mihir and Purva had an argument for the first time. It is also revealed that Jigna's death happened by an accident which encountered her. Karan manages to find out that Shamar was responsible for the accident, eventhough he didn't intend to do so. He tells Smriti about this, and acceding to her request, Karan decides to keep the secret between them. But, Akashi starts to have thoughts whether Shamar was responsible for Jigna's death, since she notices a piece of a girl's dress stuck in Shamar's car. More evidence points towards Shamar, as Akashi finds out that the piece of cloth she found is a piece of Jigna's dress indeed. An upset Bhavesh goes to the spot of Jigna's death and breaks down. Shamar is hurt on seeing Bhavesh weak on his knees and offers to take him back to the Sanghvi house in his taxi. Mihir gives Shamar the taxi charge. But Shamar doesn't accept it and says that Bhavesh is his wife's sister's future husband and he won't take money relatives. Mihir, stunned by these words, watches Shamar stamp out of the house.
Bhavesh refuses to believe Mihir when he tries tells him the Jigna's death was accidental. Bhavesh blames Shamar and after finding out about the piece of cloth, and gets the police to arrest him. However, Bhavesh later on realizes his msitake and begins to understand that Shamar wasn't responsible for Jigna's death. Hereby it is revealed only to the viewers, that Karan is evil and only wants to destroy the living of the four sisters. He is also angry with Mihir and Bhavesh for unknown reasons. Meanwhile, Mihir consoles an upset Purva, who is worried about the hearing at court soon. Smriti too is worried about the drastic change in Karan's behavior. She decides to find out the reason behind the same. Akashi is forced to go to Kshitij for help as she can't find another lawyer. Kshitij agrees on one condition, that he shall not take any money but if he wins the case, Akashi will have to spend the night with him. After having no other choice, Akashi agrees, making Kshitij have more hopes that he can win her back. Akashi is extremely upset and doesn't attend the Navratri pooja held at the Sanghvi house. Gomti ( Shamar's mother) notices Akashi upset and questions her. Akashi hides the truth from her and assures her of getting Shamar out of prison soon. Purva misses Akashi as she performs the Navratri pooja with Smriti and Anokhi.
Everyone gets stunned to see Akashi joining them for the pooja. Anokhi taunts Akashi continuously about Shamar killing Jigna. Akashi prays to God to protect Shamar and his family. Here, it is revealed that Karan was Jigna's murderer and that Jigna had been his girlfriend. Shamar tells Akashi that he has a gut feeling about something bad. Akashi reassures him that everything will be alright. Kshitij presents Jigna's original postmortem reports in the court, which indicate that her death was not caused due to an accident with a vehicle. The doctor testifies in the court, saying that he changed the original report as he was given a bribe of Rs. 15 lakh. Everyone is stunned. Jigna's original postmortem report indicates that she was under the influence of drugs at the time of her death. The court gives Shamar the benefit of doubt, and he is released. The police are ordered to re-investigate Jigna's case. This had been the first time Mihir lost a case, and he feels that Shamar is innocent and that someone gave drugs to Jigna and left her on the bridge, so that she would hit an oncoming vehicle and her death would seem like an accident. Karan recalls how he got Jigna intoxicated and then pushed her on the bridge in front of an oncoming car, which happened to be Shamar's. Mihir promises Bhavesh to find Jigna's killer and get him punished. Purva is happy to see Mihir apologising to Shamar.
Kshitij is very happy thinking that Akashi would be with him soon. Purva notices that Akashi is worried and upset. When Purva questions her, she makes an excuse and quickly changes the topic. Bhavesh vows to find out who killed Jigna and Anokhi promises to stand by him and support him and the two share a romantic moment. Karan is upset that his plan did not succeed even after killing Jigna and vows to take revenge on the sisters at any cost. Shamar notices that Akashi is upset and questions her. Akashi responds him with another excuse. Akashi is happy when Shamar presents her with a surprise gift of bangles. Akashi tells Shamar to go to Purva's house for the pooja, telling him that she will join him later as she is going to the temple. Akashi hides a bottle of poison in her pocket. She gets extremely upset and breaks down at the temple. Later, Kshitij is happy to see Akashi at his place, and invites her in. Akashi is stunned to see that Kshitij has decorated his house for her, with her favourite flowers and food. Akashi is disgusted when Kshitij tries to get close to her. Kshitij tries to rape Akashi, and is very close to doing so, nevertheless she is saved by Purva, as Purva heard her praying at the temple and decides to follow her. Purva slaps Kshitij an Akashi apologises to Purva for her deed. A happy, forgiving Purva takes Akashi along to the Sanghvi house. Akashi reaches there and is overjoyed to see Shamar and hugs him in front of everyone, however Purva cues her not to tell anyone anything. An upset Anokhi apologises to Akashi and the sisters re-unite and begin celebrating.
Karan gets angry to see the sisters happy together. Mihir starts to doubt Karan as he saw a scar on Aastha's hand which they both give different reasons to. After a few more investigations and a confrontation with Karan, Mihir finds out that Aastha is Smriti and sets out to rescue her and the two patch up. However, Purva is pregnant and she tries to tell this news to Mihir. But every time she tries to, she misses the opportunity. One day, Akashi claims that she saw Mihir and Aastha together. Purva refuses to believe her and slaps her instead. Eventually Purva finds out the truth. Karan kidnaps her upon realizing this. He tries to stab Purva but at the stroke of time, Mihir arrives with the police and gets Karan arrested. All the sisters find out Aastha is Smirti and are reunited. They bring her to her original home but Kamini isn't happy because she thinks it will create a rift between Purva and Mihir's relationship. She still mistreats Smriti and doesn't like her at all.
Hell breaks loose when Mihir's aunt Bhupath (Bhoopathi in Tamil) comes to stay for a while, as she is a bitter and stubborn woman. She constantly ill treats Smriti along with Kamini. Purva and Mihir are helpless. Bhupath keeps blaming Smriti for things she has not done. She accuses Smriti of trying to harm Prem, which leaves Kamini in doubts as Smriti would never harm her own child. Later Smriti is proved to be innocent and Kamini and Shalaka apologise her for everything and send Aunt Bhupath back home.
But more problems arise when Karan returns again and pretends to be insane, however everyone finds out later and send him away. Prem's first birthday arrives with Mihir not being there for it, upsetting Purva and Smriti to a great deal. Shamal gets sick and tired of his work and seeing that he hardly gets any salary, thinks of joining his friend Rakesh into smuggling. His manager is Goyal who Mihir is against. Shamar gets diamond earrings for Akashi from Goyal and says that they are fake. Purva finds one of the earrings and shows it to Kamini who says that they are real. Purva gets suspicious and takes the earring to their jeweller and the jeweller declares that they are a rare African type. Purva figures out that Shamar is smuggling and he also admits it in front of her. Purva says that she will tell Akashi but Shamar says that he will never let this happen leaving Purva speechless. Shamal buys a new car.
A new servant Rama arrives to the Sanghvi house. She loses her daughter Puchki because her husband, a wicked man kidnaps her. While everyone gets worried, Puchki also gets run over by a car and dies. Rama is really upset and blames it all on Purva because Rama thinks she lost Puchki in the first place when she really didn't. Everyone knows that it is an accident however, Rama believes it was all Purva's fault. After a few days they all find out that Puchki is in hospital and alive, and Rama feels bad. Unfortunately, Puchki dies of her injuries. Rama goes mad because Puchki was her life. Therefore, in return she demanded Purva to give Prem to her. The families plan on to give Prem to her because they can't do anything about it and they all believed that it was Purva's fault. In the meantime everybody plans a goodbye party for Prem and are very upset to leave him. Later they find out that the girl whom they thought was Puchki wasn't her and that Puchki was alive as Akashi visits the Sanghvi house one day claiming that she saw Puchki while she was out shopping, but she got into a car with a man who turns out to be her father who wanted to sell her for money. Mihir searches a Godown where they find Puchki. A fight occurs and Mihir is badly hurt, whereas Rama dies. Rama's last wish states that Puchki's guardian is Purva and apologises to her as her last breath went. Therefore, Mihir and Purva decide to adopt Puchki.
Akashi and Shamar are happy to find out that she is pregnant. However, one day Akashi meets up with her old friend Viren. Shamar get jealous on seeing them interact. Viren seemingly get close to Akashi much to Shamar's anger. Their misunderstandings get worse and Akashi threatens to abort her child. Purva tries to stop her and requests Shamar to stop her, but he refuses. Purva asks Mihir to help her stop Akashi. Shamar confronts Viren and blames him for ruining his life. He is shocked to meet Viren’s girlfriend – Akashi. He then figures out that Viren's girlfriend is not his wife and therefore feels bad for shouting at her. He realises his mistake and rushes to stop Akashi from aborting their child. Purva then tells Shamal that Akashi has already left for the hospital. He races behind Purva and Mihir to stop her. The family reaches too late to stop Akashi.
Smriti soon gets a new job and starts working under a man called Jay. They have unpleasant encounters at first, nevertheless they soon get along and become good friends. Jay is a widower and has a daughter of around 21 years by the name of Nisha. Nisha begins working at Mihir's office as his secretary and starts developing feelings for him. However she is heartbroken when she finds out that Mihir is married. However she doesn't give up and vows to make Mihir her man. Therefore, Nisha plans to spend more time with Mihir in order to get closer to him. One day, she pretends that her car has broken down and asks Mihir if she can spend the night at his place to which Mihir agrees. Jay shares his concern to Smriti about Nisha’s changed behaviour. Smriti assures him that she will try speaking to Nisha. Nisha gets upset after seeing Mihir’s concern for Purva.
Purva asks Akashi why she went ahead with the abortion. Shamar breaks down thinking about Akashi's abortion and after realizing his mistake, he tells Goyal that he won’t work with him anymore. Goyal, upset threatens to kill him if he leaves and puts Shamarl at gun point. Fortunately, Mihir reaches just in time and threatens to reveal all of Goyal’s wrongdoings to the police and takes Shamar away unscathed. Shamar apologises to Mihir and thanks him for saving his life. Later Shamar finds out that Akashi hasn’t aborted their child. He apologises to her but she refuses to speak to him. Meanwhile, Nisha decorates Mihir's cabin. and waits anxiously for him. Mihir is surprised to see his office decorated very beautifully. Nisha confesses her love to Mihir, which leaves him shocked. Mihir tells Nisha that he doesn’t love her and slaps her when she insists that he is unhappy with Purva. She threatens to commit suicide. An angry Mihir asks her to leave immediately.
Shamar discards everything he had bought with Goyal’s money, including Aakashi’s earrings. He resolves to start his life afresh and lead an honest life. Purva is pleased when she sees Shamar working hard as a labourer. Shamar hands over the money he earned to Aakashi but she refuses to believe him. He breaks down, deposits the money in front of Aakashi’s photograph and asks for forgiveness. Meanwhile, Nisha tries to call Mihir but he doesn’t respond and extremely upset, she vandalizes her house. She slashes her wrist to prove her love to Mihir. A shocked Jay witnesses the whole scene. He tries to revive her and finds a letter she wrote to Mihir. Smriti is shocked when she finds out that Nisha loves Mihir and an angry Jay confronts Mihir. Purva gets offended when Jay blames Mihir for Nisha’s condition. She intervenes and reminds everyone that they need to look after Nisha right now. Later, Jay apologises to Mihir for his rudeness and Purva pacifies Jay. Nisha regains consciousness but faints again in a few moments.Nisha regains consciousness. Jay tells her that Purva looked after her all night. She apologises to everyone. Purva insists that she stay with her for a few days.
Akashi and Shamar miss each other. They reminisce about happier moments they shared together. Akashi trips and Shamar catches her just in time. They share a moment nevertheless, Akashi walks away. In order to help Shamar, Mihir and Purva loan him a rickshaw. He picks up Akashi from the hospital and resolves to win her back. Mihir thinks about Nisha and worries about her well being. He confides in Purva. Kamini and Mihir settle Nisha into their house. The family play games and everyone enjoy themselves.
Bhavesh proposes marriage to Anokhi and thrilled, she accepts. Nisha thanks the family for their hospitality and requests the family to get Smriti and Jay married. The family is thrilled. Gomti watches as Shamar tries to put together a meal for himself. She feels sorry for him and gives him some food. He begs her for forgiveness and they share an emotional moment together. Akashi watches as Shamalrdeposit his days’ earnings in front of her photograph. Shamar shares all his worries with Purva. Purva tells him that everything will be fine very soon. Akashi is delighted to hear that Shamar starts working hard day and night for a secured future for his child. Smriti comes to Purva to deliver her wedding card. Everyone congratulates her. Purva tells Akashi that she is very happy for all and also expresses her wish that everything goes well between her and Shamar's relationship. She tells Akashi that Shamar has changed a lot. Anokhi-Bhavesh and Smriti-Jay get married in a double wedding. Everyone plans for a surprise for Purva and Mihir. The couple is surprised to see the decorations in the house. They all celebrate Purva's godh bharai ceremony. Purva gets her labour pains and is taken to the hospital. Here she delivers a baby girl. The show ends as Purva names her daughter with her mother's name, Revati.