Like everyone else is saying, don't stress yourself over it.
I have two brothers, a sister, and a sister in law who is just like my biological sister.
We always hang out and sometimes pass around a phone or laptop with a nasty, gory, or just plain disturbing image, guess who always freaks out the most?
My two brothers.
I even once had a doctor tell me that when taking blood samples, it seems men handle it way worse than women.
I mean, that's not really factual information but my point is that it's not rare at all for a guy to be squeamish or to seem wimpy in certain situations. Just don't stress yourself over it, it's not a big deal.
People like and dislike things regardless of gender, for example, my brothers are terrified of spiders, but then again, so is my girlfriend.
It's all relative.