I’m curious

Harems in general have been historically all-female (or largely female) in typical submission or availability to male nobility.  A reverse harem typically flips the gender roles.  Instead of wealthy and powerful men having their pick of pretty women, it would be the well-heeled women in positions of power having their pick of handsome men who'd be well obliged to take care of themselves and their appearances to please said women. 

Harems often have a composition that leans toward the taste of their owners.  A noble with broader tastes may have partners of all shapes and sizes.  While someone who "has a type" may show that in those who make up their harem.

26 minutes ago, BlackwingAvatar said:

Harems in general have been historically all-female (or largely female) in typical submission or availability to male nobility.  A reverse harem typically flips the gender roles.  Instead of wealthy and powerful men having their pick of pretty women, it would be the well-heeled women in positions of power having their pick of handsome men who'd be well obliged to take care of themselves and their appearances to please said women. 

Harems often have a composition that leans toward the taste of their owners.  A noble with broader tastes may have partners of all shapes and sizes.  While someone who "has a type" may show that in those who make up their harem.

While this answer is correct, there is also another version I've encountered where instead of one person being the center of many wives/husbands/lovers while being the one in control, instead it's a group of people passing around a single person as a sort of shared sex toy.