An on-line tree has his parents as Charles Harry Marsland ROSS and Mary Ann Constance ATKINSON.
There is definitely a death registered in Camberwell (UK) (FreeBMD)
Sep qr 1876 ROSS Constance Mary A 41 Camberwell Vol 1d, p474
This couple are together in census entries in 1871. I am not seeing a registration of a birth in the London area for a Duncan ROSS, nor can I see Charles ROSS in 1881, but in 1891 there is a census entry for Charles Harry Marsland ROSS with a son Charles ROSS, senic (sic) artist, b 1875 Clapham
So the question - is Duncan ROSS the same person as Charles ROSS - seems doubtful as Charles Harry Marsland ROSS consistently gives his occupation as author, so it seems unlikely that by 1901 he is in the army.
However the family story told to Spirited is partly correct - there IS a couple who produced a son in 1875 and the wife died in Camberwell Uk in 1876 but are they parents of Duncan - or has the family believed what's on the on-line tree.
Judith