my father lives 1500 miles away, but we are close. we talk on the phone almost every day, when we lived in the same state i visited him almost every weekend, and after moving away he came back a couple times each year just to see me. he was very interested in my pregnancy, and my son is his first grandchild, so it was VERY strange when he seemed to have little to no interest in meeting him. like in your case, travel cost was not an issue. i wrote it off because my father has some pretty awful emotional problems and sees the world quite a bit differently, but it was still very hurtful. he finally met my son last month, nearly a year and a half after he was born.

it's impossible not to take something like this personally, because the people who are supposed to care about you should make a basic effort to care about something as important as your child. i'm sorry you have to deal with this. maybe your SO can have a frank discussion with them about why they seem uninterested. there could be something deeper involved, but some people are just sorta not that into little babies even when they are family. my sister was indifferent to mine until he was babbling and walking. my father has told me that even though he regrets not visiting sooner, he's glad that he got to see the kiddo at such a fun age. if they can only visit once a year, for example, they might be waiting until your baby can interact more so they can get the most out of their visit. or like you said, it might not be a priority for them, which is obviously hurtful. i don't think it's too much to ask of our family members to at least entertain the idea of being interested in a new baby! regardless, i don't think you're overreacting and your feelings are valid