Thankyou for responding to my query. To answer your questions:-
Same tree. Not a known relative.
Copyright notice on site - yes.
Looking initially for it to be removed. If the person was sufficiently servile might accept an aknowledgement.
Our family name is almost unique there is no way this work is not original (and the name is not shared by the individual in question).
There are identifiers in the tree which indicate it has been copied across verbatim.
It is my guess that as he is boasting about the size of the tree he has assembled ours is not the only one he has attached to his own having established some vague peripheral connection.
Finally there is no intention of firing off 'heavy' threats, I think that would resolve nothing.