Is it normal i think its funny my girlfriend's brother in law hates me?

I found out from my girlfriend a long time ago that her brother in law hates me because of the gifts I get her and I think its funny.

I first found out a couple years ago when for valentines day I got her a giant 6ft teddy bear. She told me her brother in law got pissed as hell, because he only got his wife(her older sister) a box of chocolates.

It's been like that ever since, he thinks I'm a rich prick because of the gifts I give her, and that he doesn't get his wife anything.
I'm not rich I'm just good at bargain hunting, I found a discount jewelry site, I bought the bear and stuffed it myself, I get to stay on military bases for cheap vacations ect... I'm good at making my money stretch.

The thing is I actually find it funny. I don't think I would've ever cared except my girlfriend actually makes a point of showing it up in her sisters face, as way of getting back at her for crap the older sister said when they were growing up about how she was gonna make it big and leave her family in the dust ect, and she hates her brother in law.

For some reason I think its funny IIN?