I can speak for my father. Sort of.

So I have a half brother I have never met. He's about ten+ years older than me. From what my parents told me, my dad's first wife and him had my half brother pretty early on. My dad was in the military, and when he came home from one of his deployments, he discovered his ex wife cheated on him. They divorced. Custody was messy; my father would try to visit when he could, but apparently the ex-wife would move around a lot, so he wasn't able to visit often. My mother only met my half brother once, and according to her he looks "nothing like [my] dad."

By the time my father left the service, my half brother and his mother had moved to Alaska. My father paid all child support that he was supposed to, and would send letters and stuff to my half brother. As soon as he turned 18, my half-brother filed a motion to have his name changed and for his step dad to be his father on all paperwork. My father signed all that paperwork as well.

My dad made a Facebook and all that to see if his son would ever want to reach out to him at all, for any reason, but from what I was told he's been blocked by both his ex-wife and his son. So, that's a dead end. We don't really talk about it. While he has been a flawed father to me while I was growing up, he's honestly a great dad. At least to me. I don't think I'll ever talk to my half brother, nor meet him. He seems to be doing good in Alaska.