THE CHIPMUNKS ARE THE CHIPETTES BROTHERS AND THE CHIPETTES ARE THE CHIPMUNKS SISTERS

Well, kinda.

In the 80s and 2015 show, they weren't, The Chipettes live with Miss Miller.

But in the cgi movies, you're correct, they lived with Dave. But they're only siblings through adoption, and The Chipmunks are the only ones legally adopted (in the road chip).