<human>: If this is the wrong place for this post, I'm sorry. Please direct me to a more appropriate subreddit.

But anyway, my brother, we'll call him Jack, has been in a relationship with a girl, we'll call her Macy, for five years. They began to date in high school as senior and freshmen. Once she graduated she got into a huge fight with her mom and ended up living with my brother, my mom, and I. 

Over these five years, Macy has ran Jack's life. She parties and lies and cheats on him, but because Jack is so nice he treats her like a princess. She continues to party without Jack and with other guys. She ultimately makes Jack hate his life.

 Fast forward to January 4th. Shit hits the fan and they break up. Jack's friends try to tell him that they shouldn't get back together because of all she has done. 

Jack doesn't believe them because in the beginning none of his friends liked Macy and tried to get them to break up, so Jack thinks that it's just a repeat. 

Jack had a ring halfway paid off and was going to propose on their anniversary in February.

They are still broken up, and everyone hates Macy except Jack and a few select others. He claims to love her and still wants her back. I am really bitter towards Macy because she hurt my brother in such a huge way. Macy is currently living with her mother, and I told my mother that I refuse to live in the same house as Macy. If her and Jack get back together, then I am out. 

My question is, should I try to tell Jack about everything? Should I try to get involved in this shitstorm? Part of me feels like he needs to make his own decisions, but how can I let him make one so self-destructive?

Can you give me the gist of the text in a nutshell?
<bot>: My brother has been in a five year relationship and recently broke up. He wants her back but she won't change her ways. Should I get involved?