Rishivanshi rajputs are considered to be progeny of Rishi/saints and Kshatriya, also known as Brahmin Kshtriya.
There are several theories regarding the origin of the Rishivanshi Rajputs, According to A. H. Bingley, Caste, tribes & culture of Rajputs, Ess Ess Publications, 1978 which is also substantiated by the folklore narratives of Rishivanshi Rajputs, that they are the descendants of the Rishi (Saint) Shringa and his wife Shanta's. As per the folk traditions Shanta was from Raghuvansha clan and was princess of Raghukul, therefore, the son of Rishi Shringa and Shanta became a Rishivansha Kshtriya. Henceforth, 'Sengar' clan of Rajputs which is of 'Shringya' or its further dileanation into 'Sengar', thus, 'Sengar' are considered to be Rishivanshi Kshtriyas.
Another Rajput tradition believes that Sengar come from Gautam gotra, where rishi Gautam who is one of the seven Saptarishi was their ancestor, therefore, Sengar claim to have Gautam gotra.