Wouldn’t UK citizenship be conferred by his father. Sorry, I am sure you answered this before and I believe it had to do with proof by way of a BC.
Thanks.
Yes, at that time citizenship would have to be conferred by his father but it required LEGITIMACY which means a Valid marriage NOT A VOID MARRIAGE.
There are various laws that have been enacted since his birth that would have an effect..such as a law about polygamous marriages before a certain date if said person was domiciled in the UK or similiar (such as the US).
It is a MESS. Nobody is going to touch that awful mess of his life.
You are not going to get him thrown out based on his UK citizenship....unless he actually registered and/or ran around with a UK passport...anything that tries to get him thrown out on an “automatic citizenship” is doomed to fail.