Dd2 only stopped wearing night time pull ups last year at 7. She still has nights every few months that she will wet, but very rare (finally).
DS was dry over night by 2. But does have the rare accident. We are having other issues now though :/

I can only imagine how fun this will be, but my advice is to tell the certain other people in his life to back off. It's only an issue for him because they are making it an issue. And I really don't know any way to fix that (that would work).