That is my hope too Coley, that you can find some way to relate to SIL and bro in a healthy way.
If you decide to opt out of the family dysfunctional dance, relapsing (getting emotionally caught up) is part of recovery (reacting in an assertive way). Also remember, it is easy for family to push your buttons because they are the ones who installed them. Be aware of the game playing and avoid getting involved. It gets easier with practice.