I actually know of twins named
Brian and
Brianna. They were a high school teacher's kids. I think they're completely awful, they literally gave their kids the same name. That reminds me, my mom and her brother are
Michael and
Michelle. I dislike sibling names even starting with the same letter, so I really don't understand this.
I don't like any of the variants. I do like
Brenna and
Brennan, but those are different. They seem fresher and less worn out than Brian/Briana/etc.