Loving all the Bertrand questions! Unfortunately, if Bertrand wasn't killed when Isabelle was an infant, the strain between him and Alec would only lead to more distance and it would only be a matter of time before it came to a head—probably with Bertrand trying something with Isabelle and Alec either killing him then or asserting dominance in a way that would make it very clear he's not the pushover little brother anymore. Bertrand doesn't have it in him to submit and would struggle to accept equality. Their relationship would never be as close as it once was, and the power struggle would either force them apart or turn very destructive.

It occurs to me that that would be a great setup for Alec moving to the US....