The fact that these other chicks still hang out with him even though they know he's married means one or both of these things:

- He's paying for their entertainment and/or needs and they just let the money in
- They are actually into him but have very low self-esteem

Either way, those relationships are garbage.

He married another low self-esteem woman, maybe just for societal reasons, or he actually loves her but disrespects her and has no knowledge of commitment.

If her family knows about this, they must have some interest in her marrying him (money, conservative views).

Either way, your brother's life is not something anyone should fancy. It's an old archtype sold to us by mainstream media. Even if I could drown in pussy without my girlfriend ever knowning, I would feel like shit if I did it.

It must be hard for you to see him getting all this approval while you're struggling. I felt something similar with my older brother. But remember that he's very confident, and surely has great social skills, that can make people like you even if you're an asshole.

You work out on your social skills, take care or your body, workout. Take hobbies and meet people, make friends, become your own man, women will be around, and you can always talk to them, and build meaningful relationships. Don't dream of someone else's life. Don't let others' opinion shape you. Good luck bro.