This seems like a pattern. My MIL and BIL also love to tell DH that he doesn't "love Skids enough" and doesn't do enough for them. In response, they both intervene and make plans directly with Skids without telling DH. In MIL's words, "SSs need to know they are loved!" as if DH doesn't show them that. BIL also got involved with BM's scheme to reduce DH's time at the last mediation. DH told BIL that he was hurt and BM was manipulating him, BIL's response was that DH was just "at war" with BM and he needs to realize that "she is a good person." Um, too bad multiple counselors who met both of them believed otherwise, one telling DH "divorce will be good for you because she's abusive." Also, BM really wanted more money at the mediation. Once she got more CS, all of a sudden, Skids were "cured" of the "trauma" we were causing them at our house and could go back to the original schedule. It's so infuriating. I spend the bare minimum amount of time with all of them. DH feels conflicted. He is hurt by them and asked for apologies and they both refused, but he still believes they are "family" so he can't give up on them. It blows my mind that people whose lives are mininimally impacted by a divorce have held on to being angry about it for nearly a decade. I thnk MIL is a bit of a narc though and DH's divorce made her look bad, so she can't possibly move on. 

But his brothers and sisters, both half and full, have shunned Chef and me,  totally buying the Girhippo clan narrative.

Which is ironic because the Gir clan would often avoid and leave out Chef's family in everything when they were married. 

Thank God DH's parents and other family see BM exactly for who she is and they support DH in his semi-drop rope approach. BM was like this during DH's relationship though, so they witnessed her behavior firsthand and have been on the receiving end of many of her allegations. They know that the outcome would never be different, no matter how hard DH tries, with BM in charge. Oddly, BM really likes DH's grandparents and mails them cards and pictures from SS, which is funny because DH's grandparents hate her most. 

My MIL is a problem for other reasons, but we rarely talk to her. MIL had my two BILs from a previous marriage and they are the golden children, but DH, the only child from her second marriage, is dirt. After she divorced FIL 10 years ago, she has bounced from relationship to relationship, never being single for more than a week. She moved in with her current BF two months after meeting online. We can't figure out why she avoids DH, but it is the way it is. DH doesn't try to have a relationship with her, which she does blame me for, and occasionally BILs give us crap about it. Luckily, BILs are starting to experience the same stuff that DH has faced for years, so they are opening their eyes a bit, although still making excuses for MIL's behavior. And because MIL is all about MIL and can't play nice with others, she refuses to attend any events where my parents, FIL, or DH's grandparents will be, meaning no birthday parties, holidays, etc. I can handle MIL for the once or twice per year we have to interact. 

"DH and I have a pretty peaceful and successful life so they band together to attack us and bring us down to their level."

That seems to be the trigger. DH and I had a second baby, built a new house and bought two brand new vehicles all around the same time and that seemed to hugely trigger MIL and SIL. It's not like we were throwing it in their faces either. 

BOTH Husbands parents are deceased, MIL was fading away when we met, so I never really got to experience that.

SILs pretty much dont care that much to be involved in Skids life. Add to that the fact that SD23 Feral Forger has made accusations against a few of them...