Sister in abusive relationship and needs help

[wakijaki09]

It's a long one....
My sister is 19 and been with a boy since she was in school. My dad has told me before there had been abuse in the relationship but now he has her boyfriend living in the house with them. My son moved in with my dad last year and has formed a close bond with his auntie as they are similar ages.
Last night my son calls me in a panic saying my sister called the police on her boyfriend after he yet again was violent towards her and tried strangling her. Boyfriend had run off but my son was upset as he had witnessed him previously being aggressive towards her and tried to calm him down. But since then my sister has opened up to him about how it's been going on since the beginning and how police were called when she was still at school.
He wanted my advice as he knows an ex of mine went to prison for the same thing. He then said boyfriend had snuck back in house and was in sisters bedroom but she had gone out to clear her head.
I called my dad and said wtf is going on under your roof that she is getting attacked in her own home whilst her dad, 2 brothers and my son are there and no one is doing anything.
He said he knew stuff had gone on but thought they were past it now as living together. He knew police had been there and that boyfriend was still in sisters bedroom.
His words where..if he carries on like this he will have to go home.
I said dad..he's been violent towards her for 3 years, she's called the police several times, he's kicked her bedroom door in and choked her..he needs to go now!
He said he would go home and sort it out.
In the meantime I called my son back and said dad doesn't seem very bothered but is on his way home to sort it out. My son then gets really worked up and runs upstairs to confront boyfriend and throw him out.
What he didn't know was sister was back home and in room with boyfriend when he went bursting through the door so she got in the middle to protect boyfriend.
My elder brother then got involved to calm my son and then removed the boyfriend from the house .
Son then called upset as sister had gone after the boyfriend, brothers gone to Thier bedrooms and my dad trying to calm boyfriend down on phone and sort him somewhere to stay for the night.
I don't think my son has handled it the correct way as I told him to let my dad deal with it..but didn't think my dad was willing tbh.
I live 200 miles away and only really connected with my dad and siblings a few years ago but I'm just so shocked that he would be letting this go on. Aibu to have called him out over not protecting her?!

I think yanbu to be clear to your ds and to your dad that strangling is a huge warning sign of the most dangerous form of domestic abuse.

I'm not sure whether your dad will act in a helpful way, but to an extent you can't really control that.

You could share some resources with your ds that help people who know someone experiencing domestic abuse. Women's aid usually have things on their website. It is probably quite stressful for him. And I suppose he is the one you have more responsibility for, although I imagine you're very worried about your sister. She might not yet be ready to acknowledge the issue.

How old is your ds?

And how close are you to your sister?

Of course we all know that this relationship absolutely has to end, but it is how the advise comes across that is crucial at this point in your dsis life.

She needs to know she has an outlet, perhaps you could be that person. Do not tell her what to do, guide her.

And I dont think this is fair on your ds either.

I've tried to explain to ds (23) that it's very complicated and she might not thank him for intervening. He loved it at first as they spent a lot of time together the 3 of them but once he witnessed the arguements and how aggressive boyf was being he said he has withdrawn from the trio as wants nothing to do with someone like that..also with what dsis has since told him.
He said boyf won't do anything when my elder brother (22) is home and my dad turns a blind out or is out a lot. But that both him and younger brother (15) have tried calming boyf down on occasions.
I told ds that she needs support and counseling to be able to see it's not healthy and she needs out.
But I'm angry and frustrated at my dad as I can remember him telling me when she was at school that boyf was banned from house for being violent towards her. And she is such a teeny little thing.
I know no one can stop the relationship but she should feel safe in her own home with 4 other males there.

@isthismylifenow I'm not very close to sister as only really met her 8 or so years ago and there is 25 years and 200 miles between us. So only see my dad and siblings maybe twice a year for a brief catch up.
I know when I went through it the best thing that happened was the police sending a domestic violence support worker to me for counseling and to help me to take it to trial. Because like with my sister...it felt like everyone turned a blind eye and didn't want to get involved or were scared of him.