His son is and should be his priority. I understand it's disappointing, but his son comes first. I would say it's a tad bit selfish, but mostly disappointment. Knowing he has a son you should realize it's a package deal and his child is most important to him. Celebrate on a different day with him.

It's natural to be disappointed.  That said, knowing he has a child, you know he comes as a "package deal."  No matter how much he may care about you, his child has to come first.  Do you really want to be with a guy that doesn't put his child first?

I guess it's people with nothing better or more constructive to do.