Una Mary Ross, 26th Baroness de Ros of Helmsley (born Lady Una Mary Dawson) (5 October 1879 – 9 October 1956) succeeded her mother to the title in 1943. She was the daughter of Anthony Lucius Dawson, 3rd Earl of Dartrey and Mary Dawson, who held the barony in her own right.
The 26th Baroness married Arthur John Ross (killed in action 1917) on 30 July 1904, and they had at least two children:
Lieutenant Commander The Hon. Peter Ross, RN (8 August 1906 – 1940 [killed on active service]), married on 10 September 1929 to The Hon. Angela Dixon, from whom descends the current holders of the title:
Georgiana Maxwell, 27th Baroness de Ros (1933–1983)
Hon. Rosemary Ross (born 14 January 1937), married in 1973 to Beresford Osborne, and had:
Joanna Elizabeth Osborne (born 1975), unmarried and without issue
The Hon. Charles Dudley Anthony Ross (5 October 1907 – 1976), married firstly on 31 August 1940 to Lady Elizabeth Jocelyn (died 1982) and secondly in 1953 to Mary Margaret Graham (died 1994), without issue, and had by first wife:
Anthony Arthur Ross (born 27 July 1941), married in 1969 to Joan Cahn, and had:
Zara Gail Ross (born 1971), married in 1994 to Stephen Mark Sanders, and had:
Devon James Sanders (1995)
Jadon Dean Sanders (1996)
Brandon Michael Sanders (1998)
Deborah Kim Ross (born 1972), unmarried and had:
Taylor Jade Ross (1999)
