He was a son of Charles Stewart Carstairs (2 August 1865 – 9 July 1928), a noted American art dealer who was chairman of the board of M. Knoedler, and his wife, the former Esther Holmes Hazeltine (29 April 1864 – 15 January 1907). He had three siblings: diplomatic attaché Charles Haseltine Carstairs (August, 1886-26 October 1919), James Stewart Carstairs (2 June 1890 – 20 September 1932), an artist; and socialite Elizabeth Haseltine "Lily" Carstairs, (aka Mrs. John Henry Towers, Mrs. Martin Brown Saportas; 2 November 1892-April, 1977).
Carstairs wrote the book A Generation Missing, his memoir of the conflict, which was published in 1930.
He married, 20 March 1924, Susan Burks Yuille (5 April 1901 – 28 June 1978). Susan Burks' sister was married to Richard Wyndham-Quin, 6th Earl of Dunraven, and Susan Burks was the aunt of Thady Wyndham-Quin, 7th Earl of Dunraven. Carroll and Burks Carstairs had no children.
- Carstairs, Carroll (1989) . A Generation Missing. Strong Oak Press with Tom Donovan Publishing. p. iii. ISBN 1-871048-02-8.
- "Singing in the mud". The Spectator. 20 January 2007. Retrieved 4 May 2008.
- Rintoul, M. C. (1993). Dictionary of Real People and Places in Fiction. Taylor & Francis. p. 280. ISBN 0-415-05999-2.