Reconciliation with family after fallout

I've got a somewhat unique situation I could use some input on. My husband went to his sister and admitted he was having an emotional affairs with a co worker. Instead of holding him accountable and assisting him with healing his marriage, she dropped the bomb that she was having a fully involved affair with her neighbor. She expected him to not tell me about her affair as well. It went downhill fast from there and after a few really heated text exchanges, we are hardly talking to her. We are about a year out from D-Day and would like to have the issue with the family resolved sooner than later, but I am anxious about him falling into old patterns with his family.

There's so many layers to my in-laws and the issues that have built up over the years. Initially it was small things - My husband had specifically moved across the country to get away from his family and we when we moved back to his hometown, those little things about them became big things. We'd found out years ago that he and his sister were not his fathers children and not even full siblings, something his father continues to deny, even when confronted with DNA tests. From what we can tell, both of them are affair babies. As all of this is going on, his mom began a slow mental decline. Her story is that his dad is a half demon who impregnated her with donor sperm because he sterile like a mule. We've never really got a straight answer from either of them. After a bad conversation with his mother about her homophobia, their relationship with her went to shit. We haven't really had any contact with her in about 4 years.

According to my SIL's justifications, this was when they both fell into this "mistake". Wrong answer for my husband because he had another affair that had gone back years before. But my SIL continued to justify her affair with that reasoning along with that fact that her husband wasn't sexually interested in her and they were more like roommates.
She's texted me some pretty horrible stuff and my psychiatrist went so far as to call her dangerous. Another friend called her psychotic after reading some of the messages.

My husband is super upset about this whole things and after i told him the only safe way I see to proceed is family therapy, he suggested that to her. She's open to the idea, but I've also asked him to talk with our marriage psychiatrist before we move forward. Am I walking into danger? Should I just keep as much space as possible?

This is one of those times where I need an adulter-adult than me, but all my elders are gone....Help!

1 comment posted: Friday, June 12th, 2026