What should I tell my best friend?

Hey guys I really need legit advice on what to do in this situation. I have a friend I’ve been friends with for close to 12 years now. I consider him to be my best friend. The closest thing to a brother I can have. We’ve always been really tight And have been there For each other when things have been rough. I’m 24 years old he’s 23 years old. He has a girlfriend who is currently 20 years old. I really don’t like his Girlfriend because I think she’s super controlling and doesn’t let him go out and enjoy life. Since she’s not 21 She can’t really do much. A lot of the times we can’t go out to any place unless she comes if she can’t go, then he can’t. Recently from my 24th birthday. I had invited my best friend to the park for a DJ event in LA. it had a live DJ, great food trucks and great mini shops to look around. I was very heartbroken when he told me “no” to attending. he said “ it’s disrespectful to my relationship if I go to an event like that “ I was shocked because I just thought to myself “ What about our Friendship” I was heartbroken. This isn’t the first time he’s done this every time our friend group wants to go out He can’t go because she can’t go. Sometimes it’s not even a bar or a club sometimes it’s just a 21+ event and he still is obligated to not go. Hundreds of times. Couple months past later And he asked me a question? He had the audacity to ask if I wanted to come celebrate her 21st birthday party at a club in Vegas. I know this sounds like some high school drama, but I need some advice on how to tell him no And that he’s in a very toxic relationship. Thanks

What should I tell my best friend?
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