My TB mare Callie was so happy when it was she and 10 geldings.
She always in herds paired off with a chestnut "bad boy" for protection.
My male horse, he hates the "G" word, always has a domineering mare take care of him, a 18.2 hand mare at one barn (who beat up all other geldings) and now a nice little 14.3 mare who bosses him around and protects him. Cloudy refused to buddy up with a nice buckskin gelding and a nice arab gelding at 2 different barns.
Depends on the horses. Some are just mean and cannot get along with any horses, geldings or mares. Herd dynamics are so different. My mare and gelding got along with each other, but in herds split up, well my mare dumped him, always for chestnuts.
I'd be more concerned about the age differences. Sometimes older horses will beat up younger ones. I saw that happen at one barn, and the filly first was nearly killed by a young but very mean gelding, and later the filly turned very mean also. (I had to go rescue the filly and get her out of the fencing she had run into while the BO cursed Then i had to catch the offending gelding)
So if your boys are well behaved, all will be well, but if they start bullying her, separate them.
My mare lived in a big mixed herd the first year I owned her. It was about 10 mares and 10 geldings, and all ages, yearling and up. As long as there is enough space, it usually works out just fine.
And with a filly, they seem to stand up for themselves better than colts do. My filly has been out with her mom, my gelding, and a friend's mare since she was 8 months old. Even with mom in a different pasture, the filly still stands up for herself. The gelding and other mare have just finally started to discipline her a bit, and she is 17 months.
I love my girls. I've always said people who don't like mares as much just haven't met the right mare.
My gelding lives out 24/7 with 3 other geldings and a Haflinger mare. I'm satisfied with the arrangement. The boys are pretty easy-going and the little mare is boss. I often feel like I should be saying "mother may I" when I take my guy away from the herd.
The mare is the alpha, but one gelding a bossy boss He's always had an issue with "protecting" mares, and he will get that way sometimes. But for the most part, there are no issues, and when there are it's short-lived and not vicious.
It allllll depends on the individual horses.
When Rio was a yearling, he was out with a mare, a gelding, and a stud donkey. All was fine. From 2-5 1/2, he was with a mixed herd as well, and all was fine.
______________________________ The CoTH CYA - please consult w/your veterinarian under any and all circumstances. - ET
I tried doing 3 geldings with 1 mare and it was a mess
It didn't help that there were 2 very dominate geldings in the herd, one that was just an @ss in general.
My 2 geldings are in a mixed herd right now. It's them and 4 other mares so they each get two if they wanted but surprisingly they often go off on their own ( they're very open minded and progressive geldings )