I think it’s really a question of how recent the splinter reality happened, and how different the alternate being was.
There are minimum resolution levels in splinter universes to which one can connect.
So you can’t connect to too close a splinter cell from the one in which you have an affinity. I.e. once you find a version of a plane, you nearly always end up going back to that plane since your splinter gets aligned to that splinter.
So, my guess would be that if you had two Earths, and a person born in 1990. Then 9/11/2011 had escalated to a nuclear war, changing things dramatically, after a period of time, say 10 years the divergence would be greater the resolution limit and you could could fetch someone from boths splinters.
This is just speculation on my part. I am not an expert. It’s a guess/theory.