Q. Since Prince William’s wife Kate purportedly has Jewish maternal ancestry, is it possible that one day England will have a Jewish king?
There is a concept of Af al pi shechata Yisra’el, “Even though a Jew has sinned he is still a Jew”, but it is not likely that the former Kate Middleton (or her parents) would want this to apply.
The common-sense approach is to say that unless a person identifies as a Jew, lives as a Jew, thinks as a Jew, thrills at Jewish history and feels bound up in the Jewish destiny, they can hardly be regarded as Jewish.
Jewish identity can be and sometimes is rediscovered and regained, but it can also be lost, and this seems to be the situation with Kate Middleton and her family. (The cynics might add that it could turn out very expensive to install m’zuzot on the hundreds of doors in Buckingham Palace, plus Windsor Castle, Balmoral and all the other royal residences!)