You know about being a father. it's not so immediate, like being a mother is. Possibly there is no instinct. You need to learn it all, day by day.

He never learned. He never got to know you. He may be scared. He may think that you judge him, hate him or are angry at him.
Or maybe he never tried his father side and is really scared of disappointing you.

Of course it's just an idea.
WHat does your uncle say about his brother? He could be a link to understand your father better.

If you want to reach out for him, do it. Send a card, an e.mail, a phone call, anything. Don't expect his answer. Just do it because it is right for you, because it will make you feel better.

You never had habits with your father, he doesn't know you, but he is your father. It's a difficult situation, not everyone can face something like that.

Ask your uncle what's best for you to do.
Why not meer 'casually' at uncle's house? once, twice, even 3 or 4 times and then…. hopefully some kind of relationship will build and the 2 of you may be able to start a cautious acquaintance.

Maybe he is scared of the kids. Who knows?

Just remember that if he didn't show up doesn't necessarily mean that he doesn't care for you, but that maybe he's scared and feels the same guilt that paralyses you when you want to call and make contact.

Happy holidays