No offense but you're full of it. Been a woman long? I have been for 42 years and I'm here to tell you that a woman can drastically change her body in a year or less if she works at it. Ever heard of squats, lunges, and a leg press? Try hitting those hard for 6 months and you'll get a noticeable ass on you.
Genetics also play a part, and nearly as I can tell, those girls inherited a fair amount of ass. Kim's had a nice ass forever, and I doubt she's had implants. If she has that kind of ass, then her sister's likely share the same potential. A lot of other things affect how your ass looks too, for instance the higher the heel you wear, the more prominent your ass is.
I don't honestly care if her's is real or not, but I don't think she looks like a man regardless. She doesn't have the more delicate bone structure of her sisters, but she's quite a bit taller so that's to be expected. I do think she doesn't dress to show off her body well a lot of the time though. But she's still an attractive woman.