So in summary it looks to me as follows:
1. Your 1861 census find (Bardfield End Green, Thaxted) with parents William & Susan and children including Charles 12 and George 9 is the correct family.
2. Susan's maiden name was either Rolph (per Charles' 1848 birth reg) or Ralph (per George 1851 & other children), but marriage not yet found.
3. The 1851 birth of a Charles with mmn Collin/Collen is a red herring - different person.
4. The 1939 death in Bromley is a red herring - different person again.