Had this conversation recently with an older friend of the family:

Her: I told him (her husband) he can leave, just give me my half.

Me: Why do you get half though?

Her: I cook, I clean, I take care of him.

Me: How much do you pay in rent or for anything at all?

Her: Nothing, he pays. He's the one who works.

Me: Right, so you take care of the house that you both live in, and which he pays for. Sounds like a mutual arrangement.

Her: What do you mean?

Me: If you moved out, you would have to cook, clean AND work/pay for things, right? As would he?

Her: .....Ya, so?

Me: And as it is now, he works and pays for things, you cook and clean. It's split down the middle. Fair to both, right?

Her: I guess, ya.

Me: So if you're both equally benefiting, why do you get half of everything when you leave? You moved into HIS house!

Her: That's the way it works!

She's close to the family so I stopped there but oh my FUCK did I want to go nuts. He lived alone, she moved in (she hated where she was) and started taking care of him while he paid her way. In her mind, if she leaves she somehow gets to take half of the fruits of his life's work "just 'cause."

EDIT: I messed up by not mentioning that they have no kids together and his kids are out of the house. Also, if it wasn't clear, he owned the house before they even met.