What should I do?

m a stepmother, of a 5 year old. I used to take care of him, all last 3 summer’s since she has full custody of the kid. But out of no where he just didn’t want to come over anymore. I have two kids, and he would play with them, have that bond with them. Than out of no where the kid didn’t want to come anymore. He hasn’t come at all this summer, & we all miss him. But the dad is like whatever’ if he don’t want to come that’s on him. He’s choice’ & well ? What about my feelings my say? I miss that kid like crazy! and nor the baby momma don’t even have care to like give he’s son a call or a hi, something? Am I just being to much… should I just leave them alone