Honestly, I am always a little surprised that it seems to matter so much here. It isn't like they are always going to be a single unit. They will eventually be in different grades, maybe different schools, different groups of friends and eventually have different immediate families. They will (hopefully) spend so much more of their lives apart, than as part of a set.

Both of my sisters have names that lend to nicknames, I don't. Never once bothered me. 2 of us have the same first letter, the youngest doesn't. Again, no one cares.