Can you catch genital acne from someone that you have sex with?

Yes and no, but not for reasons that resemble how one can acquire stds. Genital acne occurs mainly due to sweating, wearing restricting clothing, and generally just not washing that area; so if you're having sex with someone, I'm sure that area will get sweaty and rather dirty, so if you don't clean yourself well with soap, then yes, you can get genital acne. This doesn't mean that it's THEIR genital acne (if one can actually be possessive about acne), it's your body's chemicals producing it.

So can you get genital acne from having sex? Yes.

Can you catch THEIR genital acne? no.