OP this could be me almost, accept it’s my daughter not my son. I don’t think it’s a boy thing either.
My daughter has sadly always been entitled, partly due to her GP. Indulgences.After she met someone , who also didn't really contact his parents either I think she thought low contact was normal. However like you they have far more contact with them and it really hurt that they would visit them and hardly spend any time with us .Both sets of parents live in the same town . They live several hours away. Always with us treading on eggshells too.
COVID-19 hasn’t helped and after a big row last summer, relations deteriorated to nothing . Except around birthday times ( theirs) She forgot her DF birthday , nothing on Father’s Day , some cards to us but generally unemotional moon pig ones. The grandchildren have no contact with us . Youngest doesn’t know us , older one does, but won’t communicate with us . I don’t blame the little ones , it’s been too long.
It hurts , really hurts. I don’t feel like sending anything to her for her birthday coming up.
So I really feel the pain you are going through. I don’t really have any solutions. Bar one suggestion. My daughter was also having therapy. I suggested we talk to an independent counsellor, a mediator who could perhaps allow us to sort out our differences . She refused but I wonder if this could work for you?
I am not sure if he is your only child . If he knew your DH from 3 then any half siblings would be presumably fairly close. Or is he an only child?
Anyway sending you
for a sad situation.