The only baptism I can find is the 1807 one with parents Alexander and Ellen in Soham.
The only marriage which comes up is the one in 1823 to Mary West when Charles born 1807 would have been 16.
The only suitable Soham baptism for Mary West is 4 Aug 1799 parents Edward and Mary (late Barret)
I can't find Charles in any of the Censuses at all but I can find Mary in 1841 and 1851
1841 HO107/73/13/F5
Eastfen Common, Soham
Mary Rankin 40 Ind. Y
Eliza 11 N
Sarah 8 Y
Fanny 1 Y
1851 HO107/1763/F164/p38
Eastfen Common, Soham
Mary Rankin 68 Married Ag Lab Soham
Eliza Rankin 20 Soham
Sarah Rankin 18 Soham
Frances Rankin 16 Soham
There are the following baptisms in Soham
Ann Rankin 16 Jan 1825 Charles (Miller) and Mary
Sarah Rankin 3 March 1833 Charles (Soldier) and Mary
Eliza Rankin 3 March 1833 Charles (Soldier) and Mary.
Possible death for Mary
Mary Rankin age 63 June 1867 Newmarket 3b 338
No death for Charles in Cambridge and no sign of any military records, nor can I see a birth reg or baptism for Frances.
Emeltee