Ours are 17 and 20. In the short term, we've gotten between them physically. When their traffic is verbal, we hit the bottom line for both of them and keep repeating it -- whether it's name-calling or manipulation or a violated boundary -- and just try to point out the damage it does rather than paying attention to the perp through blaming, etc. It's hard not sounding like we're taking sides, so we focus on the behavior and what the more vulnerable party needs ("you're screaming and looming over your sibling. that intimidates people." "you're manipulating and provoking your sibling. that use of control as a weapon is cruel and alienating." in a calm voice. while getting and staying between them.) There's a lot of talking way after the fact and after everyone's cooled down. As pp said, a LOT of listening to them -- I cannot stress that enough.
The long term approach has been our attempt to make our home respectful. We tried to live up to what they need rather than making them live up to what we need. They hear an imperative from us maybe once a year, almost exclusively about a health or safety issue, and that kind of helps maintain our moral capital.
A main reason we don't resort to threats or bribes? They would see right through us, smolder with resentment, call us on the injustice, and dismiss us completely. It's not that DH and I are highly evolved, it's that the kids are.
