P.S. Does any one know if kids who are born illegitimately and their parents later marry, does this legitimise them?
I have some knowledge of this issue from some cursory knowledge of probate law that I have.
Under British Probate Law (until 1969), an illegitimate child of a man was not a child at all under the Law, whereas the illegitimate child of a woman was a child under the Law.
If the father and mother subsequently married, this still did not make the father the Legal father (at least as far as probate law is concerned, other aspects of the Law may have been different). The father would have to legally adopt the child for it to be considered legally his child.
Probate Law does now recognise illegitimate children in both cases, though I don't think it applies to claims to Royal (or other Noble) titles.