I did not mean Peters Son, its logical that he doesnt exist anymore. I meant Peter himself. The Observers wanted this to happen, but why if his existence was crucial to their future?
September also said that he had the kid with the wrong Olivia. Which is why they changed the timeline. Bolivia & Peter are from the same Universe. Peter & Olivia are the ones that need to have that kid. They are the first to have a kid from different Universes it seems