@jespah,
Well, I've said this before and I suppose it will have no better reception this time, but it's Reality 101.
Your father and other people related to him do not want you in their lives.
Life is not fair, we don't get what we want or feel we deserve.
On the other hand, your father is getting what he wants, including no contact.
Has it occured to you this might wreck his current marriage, or at least put undue strain on it?
We can all play the "what if" game all day (what if my half siblings want to see me, what if his wife would be happy or at least ok about finding out her husband has a another child, what if because you wish it so it will happen, etc)
You could wreck his life with this. On the other hand, if you do nothing, you can have a perfectly happy life without all this, and he and all connected with him will be happy too. Yes, really you can, and probably will have a happy life even if you don't push your way into where you are not wanted.
All this guy did was act as a sperm donor. Beyond that, he's nothing to you.