We don’t actually know, to be completely honest. That secondary mutation is as much a mystery to us, the reader, as it is to Alex. Very little is known about it, as the writers haven’t chosen to expand upon it that much. I would *assume* since there was a transference of ‘Alexes’ without him really wanting that, that yes, *all* Alex’s have that ability.
But again, it’s slightly speculative?
But from what I recall, it would be safe to assume that the other Alexes do as well. I could just not be remembering it completely, but this is my answer and I’m sticking to it XD Nope! Just this one Alex has the power!
Edit: OH! AND the Alex we have seen in the AU’s ARE mutants…but that doesn’t mean all of them are. I think we’ve only met…..1? or 2?