He was the grandson of the famous inventor Hiram Maxim (also a Streatham resident) who coincidentally died 24 November but in 1916. They share the same burial plot at West Norwood Cemetery with Hiram's wife Lady Sarah Maxim
The following is from Find a Grave
He was born Eldon Maxim Joubert. However, from a young age he went by Maxim Joubert. He was born in Hyde Park, Massachusetts and was five years old when his mother died in 1907. In 1909 his father sent him to England to live with his maternal grandfather and step-grandmother.
Although he lived almost all his life in England he retained his U.S. citizenship.
The inscription on the gravestone he shares with his grandfather and step-grandmother indicates that he was a Lt. Colonel in the U.S. Army. However, no record has been found to date about his military service.
It appears that he was married two times.
In 1923, according to the 1837-2005 England and Wales Marriage Registration Index, he married Cecilie A. Follain in Marylebone, Middlesex, England. No other record of Cecilie A. (Follain) Joubert has been found.
In April 1932, he married Ivy Irene Holmes in Wandsworth, London, England. Irene was born 10 November 1899 in Henden, Middlesex, England and died on 15 February 1987 in Croydon, Greater London, England. There are several records for her in Ancestry and FamilySearch. It is not known at present if she is buried in the West Norwood Cemetery near her husband.