Every time he goes back in time and changes things, it makes a new timeline. The game specifically said that he cannot go back beyond where he already arrived nor can he keep going back to try and change a specific event. That is why he only had one chance to save Olivia. The only way the MC and his sister can exist on the original timeline is if their father existed BEFORE the time travel stuff happened. If the MC does father a child with Julia, then there really is no way he can produce the same genetic code that made himself or his twin sister.i did i just said that he hasn't been seen in past.
anyways dev solves it 1 way or other no use to debate it.
Again, it is the same thing with Chloe. Olivia died on the original timeline before she got pregnant. Therefore, Chloe wouldn't be able to find the artifact and go back in time to save her mom in the original timeline, because Chloe doesn't exist.