Is it normal to think other people's shit smells awful and my man's is ok?

I don't know if it's just me but for some reason, when I walk into a bathroom after somebody took a crap, I almost vomit because of the foul smell! Sometimes I even think my own crap smells awful but for some reason, my man's crap NEVER smells bad to me. Is it a pheremone or something? My brother in law lives with us and I can distinctly smell whether it was him or my man who was in the bathroom. I know I'm into ass licking and stuff but that's when he cleaned up properly and taking a dump is NOT clean... Why is it ONLY his crap that doesn't make me want to vomit? Any doctors on here got an answer? He's really skinny and has a very fast metabolism.