AIBU to think my ex should not be promising to see son

[Mrbojangles1]

I won't boar you too much with back story it the same as many, ex hardly sees son has not paid maintenance for about oh 10 years

My son sees is bio grandad he has countined to see his grand son dispite my ex he is a wonderful grand dad and sometimes drops buy when son is with his dad
But often he says he's coming and simply dose not show up

Today my son was on the phone to his granddad and my ex was with him so son spoke to him too said he was defiantly coming to see him at grandads in the hoildays gurrrr why dose he do it

No. It's not fair on your son if he's being disappointed all the time and your ex should realise that a promise should be kept or what kind of example is he? It's nice that your son has a good relationship with his granddad though.