It's much more heroic/angelic than your other favorites. Less human? haha
I like the name Gabriel more than I like most names I'd put in its category. Gabe is cool. I wouldn't say Gabrielle in a way that would lead to nn Gabe, though - she'd be a Gaby. I'd call a son Gabriel "Gabe" regardless of the cousin.
I wouldn't find it weird to know a family with the same sib names. Unless they were super rare, which they're not. It's just a coincidence, nothing more to think about, no need to make it awkward.
- mirfak