Even on the 1891 census Charles still states he's married but doesn't live with Sarah Ann. Would it be illegal not to register a child's birth at that time?
Hi Jenny
Even though registration was introduced in 1837 it wasn't until 1874 that it became compulsory for parents to register their child. Prior to that they had to register if the registrar asked them. From 1874 it was the parents responsibility to register rather than the registrar's duty to collect the information. As the children were all born before 1874 it is possible they weren't registered.
Even after 1874 many parents believed that baptising their child was registering them. Parents had to register the birth within, I think, 42 days of birth. If they were late they could be fined so parents quite often 'adjusted' the date of the child's birth to avoid the fine.