I was a kid when it came out, and I remember debating with friends that he was his father. I believed it because of Owen’s line about being afraid Luke had too much of his father in him. But there were a lot of kids you couldn’t accept it.
I’ve watched it twice but just can not find it for the life of me. But if you can find that vid on youtube about what was originally planned and what could have been, it’s really interesting. He put together a lot of info from old magazine interviews and the letters sent out to members from that old 80’s Star Wars official Fan Club.