Any help would be appreciated. Cowboy harem would be nice too lol
FantasyLover has a few stories with harems and farms/ranches. Not sure if any are a perfect fit.
Lazlong's Wagons Ho series has some cowboy-type stories with homesteading and harems.
Lazlong's stories are Premier Only, and those ones deal with cattle ranches rather than horse ranches. I think most of the "ranch westerns" here are cattle ranches.
Jay Cantrell had such a story - https://storiesonline.net/s/62738/the-hillside - set in the years shortly after the Civil War.
Joe J also has one - https://storiesonline.net/s/52784/el-paso-joe-j - although that one also qualifies as a "Do Over". I know he ranches cattle in that one but can't remember if he also ranches horses.
happyhugo gets in on the act - https://storiesonline.net/s/66339/saga-of-sam-jones - although the horses in that one also go "moo" and the "harem" aspect is more serial rather than parallel.