Sorry this is going to be a long one. I'm a long time lurker but first time poster. This is really worrying me and I don't want to upset anyone IRL by talking it about it 
My DH's family have had problems with my BIL since before I met him (10 years). I'm not sure exactly how long but since he was mid teens and he's 32 now. He moved away 5 years ago but is due to move back soon and my MIL is keen for us to put everything behind us, move on and have a relationship with BIL.
He's a drug addict and alcoholic, so I recognise he needs help, but he refuses it and has done so much over the years that I'd be here forever listing everything. But to give a few examples:
- He showed up at my PIL's house while they were on holiday, high on drugs. Me and DH were there. He smashed the house up, accused DH of moving his drugs, and then went for him with a meat clever. He was so high he ended up hurting himself, luckily DH was not hurt. Caused thousands ££ of damage.
- Showed up at our house, drunk and high. DH tried to calm him down, DH ended up with a dislocated hip, a broken nose and some other minor injuries. I (wrongly) started shouting at him and he ended up pushing me and I fell down the stairs. He then took the keys for my DH's car, drove off and crashed it in the next town.
- Has stolen from a lot of family members to buy drugs and alcohol, and damaged a lot of property. He makes horrible threats; to burn down houses and kill people, he has a horrible temper.
- He assualted his girlfriend, smashed up her house (including breaking all the windows while her baby was inside), then stole her car and again crashed it. He was arrested but didn't attend his court hearing. He eventually turned himself in after a warrant was issued for his arrest and he was given a conditional discharge. This is still in place.
- Ran up a load of debt while registered as living at my PIL (he's always in between houses). They ended up with bailiffs at the house. My FIL had recently had a heart attack and ended up back in hospital from the stress of it.
My MIL in particular thinks I'm unreasonable in holding a grudge. I've always respected that he's her son so I've not once said anything bad to her about him, I've just avoided any events he'll be at and ignore any mention of him. She brings him up a lot but I'm not sure if this is an attempt to get me to forgive him, or if she just needs to vent. We're close and I'm the only other female in the family so she does talk to me a lot when she's worried about things. It's usually telling me the bad stuff too, so it doesn't help move me towards forgiveness as it's just a constant chain of awful behaviour. And I care for my PIL so it whilst I don't care about him, it hurts me to see them hurt and they'd be broken if anything happened to him (prison, injury).
My DH is understanding about it all. He knows and appreciates how I feel so wouldn't expect me to have a relationship with BIL. They don't have one and rarely talk, so no worries from this side of things.
I don't want to upset my PIL but the thought of having a relationship with him makes me feel sick. I've had treatment for anxiety in the past and my MIL says that because of this I should understand that he's not well. But I've never done anything to anyone because of my anxiety, and I've taken every piece of help offered to me, so I struggle to see us as comparable.
What would you do? Should I try and build a relationship with him for the sake of my PIL, or stand my ground that the things he has done are unforgiveable to me? Should I be the one to say it or should I speak to DH and see if it's something he'd want to say on our behalf? I just don't want to upset anyone, including myself.
Sorry again that this was so long
. I'm really stressing myself out over it and needed to get it all out.