Should parents be responsible for their adult children’s behaviour?

[Lightingjolts]

Are parents responsible for their adult children’s behaviour?

A bit of a delicate topic that’s causing some divide in my life right now.
Basically my husband has a younger sibling who has a long term girlfriend. His girlfriend has never liked me and has acted out whenever anything positive has happened for my husband and I. She caused a scene at our wedding by loudly arguing with my BIL that it should be her wedding, not mine. She stormed out of my MILs house when my husband and I announced we were having a baby, to name a few examples. My MIL and FIL dislike her and have recently told my BIL as much. MIL and FIL have also voiced that they believe she is jealous of mine and my husband’s relationship, to us and to BIL. Since then, BIL has gone very cold with my husband and I. He’s started making cruel remarks to me and sending me unkind Facebook messages, leading me to blocking him as I don’t like conflict. My husband has told him to leave me be but it hasn’t fixed anything.
I’m very close with my MIL and FIL and see them regularly but whenever BIL is around, he gives me filthy looks, mutters remarks like “stupid c*w” whenever I speak, and the most recent is that he and his girlfriend have told MIL and FIL that I’ve been bullying her/his girlfriend and have sent her abusive messages. I haven’t done so and MIL and FIL have said they don’t believe it. Husband is very supportive of me.
My issue is that BIL keeps up his behaviour despite my husband sticking up for me. MIL and FIL witness it but don’t say anything. I’ve started to get upset by this and I’ve started keeping my distance from the family as a result.
My husband asked his parents why they say nothing to BIL and they’ve simply said that he’s an adult and we’re adults so it’s not their place to get involved. I absolutely see where they’re coming from but my husband disagrees.
Only thing I’m feeling down about is my options are to basically go to see the family and accept the fact I’ll be mistreated and my children will see it (BIL is rarely not there; husband’s family are very close), or not go and distance myself. I adore my MIL and FIL so this is difficult. I’m in touch with them a lot but my husband is very upset with them as he feels they’re treating me unfairly. I’m conflicted. It’s a tricky situation but curious for other people’s perspectives, especially those with adult children.

Please be kind - I’m a very sensitive person and this drama is really draining on me, and I’m just looking for the best way to move forward without damaging my relationships with anyone.

I would definitely call out his disgusting behaviour adult or not I would not have that being said to you under my roof or anywhere from a grown adult man or woman of my own.
They need to step up its disgusting basically watching and allowing bullying .

If they're brothers, why hasn't your husband knocked him out by now (figuratively). If someone was using the stupid c*w language around me they wouldn't last two minutes.

Why don’t you try and have a civilised conversation with BIL and SIL? Ask them over, have a meal and some wine and try to talk about their problems with you?
Air your feelings and possibly sort things out. You never know, it could all be resolved.

This.

They’re not responsible - ie if you stop speaking to them purely on his behaviour that’s not fair

But they can definitely call him out and ask him to leave if it happens in their home. If you stop talking to them because of their behaviour (or lack of) that’s fine. Tell them this.

Haha this is quite funny though!

Or the old “why are you calling me a stupid cow, Bob? Are you feeling quite ok??”

Imagine having guests round and allowing one of them to call the other one a stupid cow, and not chucking them out of your home?!

Oh because they sound like really rational people who will be receptive to this!

😅

I’m sorry you are dealing with such an awful family in law situation OP. As the abuse is happening in front of DH’s parents they absolutely should call this out and are being cowardly in not doing so. It’s why women get so much abuse when others simply ignore.
If it were me I would tell them all if it does not 100% stop right now you will be forced to report their slander to the police (the non existent messages) and that you will pursue it as a civil matter.
No way would I allow my children to witness this. If it happens again I would say very clearly to my children I need you to be able to recognise abuse and to know you should not and will not tolerate it. We are leaving now and I am disappointed your grandparents allow it to happen. Then do just that.