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.
Well the way I see it, the marriage thing is interesting and I would love to get to the bottom of it but, as I understand it, citizenship was conferred based on the status of the father or sperm of the father. Marriage aside, it would be the legitimate and universal recognition that status is derived by your father.
Please, no argument, just my POV.
Wouldn't acknowledgment serve as well to confer citizenship? It would in the US, and it certainly would serve to establish that his legal fatheer was not a US citizen.