I was just thinking of
Gemma a week ago. I really like it and the nn Gem. Having said that, there's something I don't like about the name when I say it and I certainly don't care for how close in sound it is to the very common
Emma. I'd be more inclined to use it for a pet which I think would be adorable.
As for a sib set, I think I'd likely use other Italian names such as
Leo and
Francesca /
Gabriella /
Marina /
Natalia or something that would blend in well where I live and not be too OTT.
Your words reveal who you think you are, but your actions prove who you really are.