Right, but the problem is that the MC gets half his genes from his mother and half his genes from . . . himself, which gets half his genes from . . . himself,. . . . It's an echoing loop that comes to no logical conclusion. I agree that time travel itself is ridiculous scientifically, but even if we accept that basic premise for this story, the fathering of oneself breaks down even within the parameters of something that defies science anyway.
What I was more speaking to wasn't that it defies actual science and math (which it ofc does), because time travel can't happen either — you can't exist before you actually exist; that's a paradox. I was using shorthand for terms to mean that even willingly suspending disbelief to accept time travel, the logic of looping endlessly into yourself (out of yourself?) is too much (for me, at least). Ignoring everything else, making something out of nothing is a bridge too far for me. That's really what I meant.