Am I in the wrong here?

So.. were do I start..
I’m 26 years old and my brother is 27. We have always had a love/hate relationship with each other. We Were bestfriends growing up.
Over the years our bond has been less and we only really speak to each other if I visit my mom’s house were he still lives.

So.. here is the problem. He now has a girlfriend and seems to act differently towards us. He still lives with my mom and he’s being really rude to my mom and almost forces her to let them hang out at out home because they both don’t have a place to stay and they are always at his girlfriends house. He is also a Christian and used to be so religious and even got baptized again 4 years ago. But he made a comment the other day that he really did not care much about that anymore (his girlfriend is not religious). He changed a lot and I think it’s all just to please his girlfriend but he is treating us so badly. He used to be so kind. So now we are fighting a lot because I keep sticking up for my mom. And I honestly don’t think his girlfriend is right for him. He is not even himself anymore.

What can I do to restore our bond and not make it worse?
Am I in the wrong here?
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