It depends on the nature of the relationship. The obvious one is parent-child, that parents get to have quite a lot to say about where and what their young ones spend time on, and with whom. Though part of growing up is pushing away a good deal of that influence, and then I guess for some, inviting a bunch of it back in if the relationship successfully transitions to a healthy adult-adult one.

But I don't think it really stops there— I would hope that my spouse, siblings, and close friends would feel comfortable enough speaking into my situation if they observed me falling into a pattern of behaviour that looked to be self-destructive. We need checks and balances in our lives other than the just the extreme end of having to stage an intervention when someone's bad enough that they're hitting rock bottom.