Let me give some background.
I have a car. My dad has a car. My brother wrecked his car. My dad gave him his car and started sharing my car (a definite downgrade, because mine's a wee cheapy). I don't mind, he's my dad, it's full of farming stuff now but c'est la vie et al. I owe him much more than a car.
So my brother wrecks my dad's car. He needs to get to work. Dad asks if he can use my car, and I agree. He doesn't have money for fuel, so I give him £20 (with my dad's promise to get it back off him, because I'm not an idiot). It's not something I want to do, for obvious reasons, but not something I felt able to say no to.
He gets pulled over by the police and is cheeky to them. They say they're going to be on the lookout for the car in future. It stinks of smoke. It's got his rubbish in it. He leaves his clothes in it. There are only fumes left in it and I have to go to a job interview.
The next day he wants to go buy something. Dad says "ask [me] if you can borrow his car." I say "where are you going?" He says "that's none of your business. I have the key in my pocket, I can just go." So after a bit where he insists he'll just take it, and he refuses to tell me where he's going, I say "no."
He turns to dad like it's his trump card. "Dad make him give me the car. I need to go in." Dad doesn't say anything, just looks angry. Probably at me. But it's a moot point, because at that point I'd rather slit the tires than let him, so it's not like appealing to his daddy would change my mind. When he realises getting the car isn't a fait accompli he starts saying "can I have the car, Pleaaase" with a sneer, gradually building up to terse but, if he'd done it at the start, acceptable asking. I still say no.
I go help my aunt at her house with some basic computer stuff, then come back over. He's taken my dad's car, which is illegal. Mum says I should have given him mine, he could lose his job if he's caught. Dad's obviously furious with me. I say that's not my problem, I'm not his mum or dad, and I don't have to do anything for him.
So today, being the day after that happened, my dad (who uses my car for local trips concerning the farm) is just giving him the key without me being consulted at all. I've asked him to stop. He didn't say anything, which means he won't. So now I'm stuck. I won't take away dad's access to the car no matter what. And he's just going to keep letting my brother use and break it, like he does everything else.
Well, stuck and incredibly annoyed/angry.
Edit: I should add that my brother is thirty. years. old.