I'm going to insist my wife stop seeing her best friend and their kids
You said you "insist" your wife stop seeing them.
Yeah I can't force her to but if she does it again I'm leaving her.
Unless she is cheating you should not be so controlling to your spouse. If you are already unhappy you should tell her.
I don't think I'm being controlling when I choose who to be with.
Yes, you are. You are making her choose between you and her best friend. That's not fair.