I'm sure mine started with my mom at a very early age.
This is probably the best way to describe it for me. I was more fascinated by girls farting when I was a little kid, then it later became a full blown fetish.
I had these fantasies when I was a little boy of being invisible and following a girl I had a huge crush on around all day, and just watching her take a shower, or maybe hear her talk about me ect... I got the idea because there was this childrens book I read at my school about a boy who could turn invisible.The more I thought about it, the more "real" it became, as in, I thought if she didnt know she was being watched, she would probably fart when she thought she was alone, or go in her bathroom and take a gigantic shit, and Id get to watch it all. The thing was, this girl was very prim and proper, so to think of doing something gross was to me, as a little boy, fascinating.
Later on when I hit puberty farting just became sexy to me. Up until a few years ago, girls pooping was just a fascination too, but Id say its more of a fetish in these past few years. I think there might even be some old old old posts I made on this forum saying I dont have a fetish for girls pooping, thats changed now lol.
Not me, but a lot of guys kind of get anxiety about this fetish and think something is wrong with them. Tell your cousin that you have it too just so he wont feel like a freak. And if you get a gassy girlfriend, ask her to fart in his face lol.