As David indicated, the younger Robert's age is given as 10 in the 1881 census. However, the 1871 census lists him at 18 mos, placing his birth in approx October 1869 which coincides with his age as given on Titanic's articles (42). His mother, the former Eliza Love, was born in Cowes c. 1845-47 and died in 1876. Robert Sr. and Eliza appear to have had three surviving children — Robert being the eldest, followed by William (c. 1872) and Ernest (c. 1874).
The 1901 census shows a Sarah Scovell, aged 57, with a 9-year-old daughter Margaret L. living in Shirley, Southampton. If these ages are correct then Sarah was over 25 years Robert's senior, and Margaret was 19 at the time of the sinking.