Hi Curtis! (or anyone who might have insight into this?)

So I remember one of Curtis's old messages talking about multiverse
theory (aka parallel universes). Curtis, you used the example of a
tragic accident happening to your daughter at a young age, but you
were able to mentally jump to a parallel universe where this incident
did not occur.

My question is... What determines which universe you "live" in? And
are we -- for all intents and purposes -- exactly the same person in
all universes? I.e. Is my brother in universe-A completely indentical
(in terms of 'who' he is) as my brother in universe-B? or is there
some inner trait that distinguishes between universe A and B? (and C
and D and E etc.)

Cheers!
Pierre