I don’t think it’s double standard as one thing is to ask about his kids and entirely different thing is asking about his ex wife as she has nothing to do with this conversation. Why would even care about his ex wife? I think if you wanted to continue conversation re his kids you could ask how old is his kid or something about him, not his ex wife.

Unless one brings the conversation up or within some specific context, people don’t tyically ask about ex spouses. Especially subordinates don’t ask supervisors

Just a learning process. Next time think if it’s a question on topic etc I don’t think your supervisor is hateful