That's a very interesting thought experiment you propose. While it would be unlikely to happen in nature, scenarios of that kind are crucial to understanding the sort of physical dynamic which exists between these parallel universes. I am inclined to believe that the emergence of the black hole in one "parallel universe" would have a substantial gravitational effect on the neighboring universes at the instant of its creation, potentially to the extent that the same black hole would emerge in each of them. By the logic of the theory, the blackhole itself would be a 4d object occupying the entirety of a 4d spherical space encompassing many "parallel universes" (so all of the "neighboring parallel universes")--but this is referencing the state of a blackhole which has already come into being. At the split second of the blackhole's creation, it's an interesting puzzle to imagine to what extent neighboring universes would be pulled in or diverge.