My brother is just like this. Maybe honestly even to an extreme past your BIL, because he cannot even maintain a friendship once the other person runs out of favors. He’s a good person, and profoundly hardworking, and he can just never understand anyone would want to be kind to him for free. I think he’s like this because of how our dad raised us, with these insane ideas about masculinity and being a “leech”. We also don’t have much of a relationship with any extended family or anything, so he’s never been accustomed to family being family together.

I always am kind to him as a grift. When the holidays come around I cook him a full dinner and package it up, and then tell him I need to come by his place so he can take a look at my car or something, and instead just drop it off. It always has to be a trick so that he doesn’t get in his head about it, and then after, he always appreciates it. We’ve gotten much closer as adults and I’ve been able to help him out when he’s needed it I think because I got so much groundwork in by tricking him. He’s more comfortable now calling and asking for help if he needs a ride to the airport for example, and not too long ago he came to stay with me at my apartment for 3 months because he didn’t have anywhere else to go to get back on his feet. He also has started to accept compliments from me in a genuine way. I’m excited for him. He’s also in therapy and I think it’s a huge reason he’s been able to get so much better as well.

I think if you take a similar approach to your BIL maybe that can work. Coming up with reasons like “you’re so good to have around; it’s a huge help when you cook dinner and how you interact with our kids. We don’t want someone else living in the basement who might be a bad influence on them, or who might damage the property, and we don’t want to lose all the profound help you offer us, which has made everything so much easier. Please stay if you’re willing, we drafted up a rent agreement if you want one that we felt was only fair given how much you do for us. Really think about it, you’d be saving us a LOT of trouble.” Framing it as being selfish on your part rather than his part might help him to feel more comfortable with it.

You have to be doing it honestly though. Don’t set up a situation where you are going to resent him or where you’re martyring yourself. The grift is only good if it’s coming from a good place to do good, which I do think is where you’re coming from, just please be careful.