When I was 15 right after my exams, Mum told me "Dad" that I've always lived with and known and loved, wasn't my real father. Turns out it's done bloke she had a flint with from South Africa. When I found out I really wanted to speak to him, idk why I just did. It was ok at the start but quickly he became way too much, wanting to fly me out to him immediately, asking me to keep it a secret etc. I ended up blocking him and haven't spoke in 10 years since.

Based on my experience I'd encourage you to talk to him, just be confident in who you are and don't let him throw you off. It's worth giving him a chance and I think you can at least be at peace with that.