Ok, so I’m a pervert!
 

We were walking back to our car after an MLS game the other night and I noticed a woman a few feet in front of me. White dress, cute little butt, and I thought to myself “wow, that looks like Gwen’s ass”. She lives in our community, she’s divorced but has a nice body. Petite, small breasts, not the type I would have prioritized back in the day, but not one I would have turned down. All of a sudden my wife yells “Gwen!”. So yes, I recognized a woman by her ass.

As a assman myself I’ve definitely taken note of the shape and movement of the asses of women I know. Obviously it’s great to have been in swimwear with many of our female friends and actually see their butt cheeks. But even women I’ve only ever seen fully clothed, I’ll take note of the appearance of their ass and try to have a good idea of what it would look like naked. How it moves when a gal walks. Happiness is a nice ass.

Me too
 

I was in a sandwich shop once and recognized my (m) partner's (f) daughter (f, obviously) by her butt from behind. I don't lust after my partner's daughter, so I didn't feel guilty or perverted.

I too have been able to ID women from the backside. I consider it a special skill that no one knows about. :)

Recognising sisters by their asses
 

I went to a wedding of one of my female friends. We are a group of a dozen friends from college, all were invited.

She had a lot of sisters none of us knew before the wedding. And she had a really gorgeous ass! :D When she introduced our group to one of her sisters one of my other female friends noticed the sister had the same fantastic butt shape as our friend.
So we started the game "tell who's a sister of the bride by looking at her ass" - and we were really successfull!

When the bride noticed she enjoyed all the attention for her butt. The whole group commented on her ass and made her compliments. Two female friends were even brave enough to grope her a bit :D