The 1851 shows Robert with Mary age 23 born Eng (?cheltenham as sisters either side were)living with parents in law at 4 King St - judging from age of last child born in Douglas (? bapt) they moved to IoM after 1831 but by 1839/40
by 1861 Charles had moved to Athol Street (found there in 1852 directory)

Robert as c/o irish born Mary Williamson (confectioner in Church Street in 1841) looks the best bet - all parties lived within a very short distance of each other