I just wanted to share a couple resources I've found on YouTube that have been incredibly helpful in dealing with DHs family and BM. And I'm assuming probably someday SD. 

The first one is called Surviving Narcissism. Here's a video from it: https://youtu.be/Vd8Hs3Rxodg

The second one is a lady named Dr Ramani.  https://youtu.be/JqK2zHZrJFU

I've been sending them to DH also and they've really been helping him wrap his head around what's going on and how to deal with it.