Should I tell my brother I don't approve of his girlfriend?

My brother started dating an old friend a few months ago. I think she might be a rebound because they got together right when he broke up with his other girlfriend and they HATED each other. It almost seems like she feels like she won something. His personality with her is different than normal. She dresses nasty. For example she once wore a shirt with her whole bra showing, and I know my brother doesn't like that. He even made a comment to my dad "that he liked how things were before." I don't think they are good for each other. I mean if I was dating a guy he didn't like he would tell me so shouldn't I do the same for him? Should I text him? I can't see him in real life or talk on the phone much he doesn't have the service. If so how do I bring it up?

If your brother didn't like who you're dating, he might say something but would you dump someone you care about just because your brother doesn't like him?

Sometimes families getting into each others business can have the unintended consequence of driving a couple closer together instead of prying them apart. In my view, life works better when we all do our very best at taking care of what we're responsible for and hope our brothers and sisters do the same.