AITAH for not doing stuff for free?

I am a trained automotive mechatronics technician and occasionally do jobs for friends and family. Generally, I don't generally charge for my services. I say: If you want to give me something, you are welcome to do so. Nevertheless, I occasionally receive a nice gift. A bag of sweets, something from my Amazon wish list, something for the cats, and sometimes money. Just a gesture of gratitude.

But I have a brother-in-law who apparently takes everything for free.

Inspection? Repairing accident damage? Diagnostic? Retrofitting parts? Nothing.

Now he wanted me to install something for him. Effort: 1-2 hours.

This time I said, "It depends on whether I get something in return this time."

Then he said that it was normal to do things for family members for free.

Am I the asshole for not wanting to do it for free this time?