You make an interesting argument but i think that's altogether a seperate premise from what you usually see in these regression comics. Though i do agree with the notion that these stories almost never take proper account of the butterfly effect.
What you're proposing would imply that changes would imply changes in the time before the carachter gets returned to the past, which would make sense in the context of time ripples, like in Flashpoint in DC, but that's usually not the case that we see here. Though i really like your idea of coming back and sunddenly having a new sibiling, that'd definitly throw somebody for a loop