Ok, we have six horses. Four are normal size and two are Shetland crosses so they are much smaller. I would really like to put all of them together so they could socialize as I hear that horses like to do, but it seems to be impossible. We will always have to keep the two Shetlands crosses away from the big horses. If they had a super large turnout area we might could put them with the big horses but I know what kind of bullies my big horses are so I won't even consider that. It's the four big horses that create a fuss. You would think that four horses, two mares and two geldings could get along in a pen that is about a half acre in size or a little larger. But NO! Star was my first horse, a small Mustang-type mare, sorrel with a few appy spots on her Then I got BlackJack, a black Morgan gelding. I had them at a stable for almost a year before we moved here, and they were used to each other. After moving here that became close stable mates. Almost like an old married couple. Then we got Sonny, a brown and white paint with quarter horse bloodlines. Sonny did not like Star and Jack and they didn't like him. He had his own pen. Then we got Nita, a bay quarter horse mare. Nita did fine with Sonny, but was madly in love with Jack. Jack liked her but still preferred Star. This seemed to make Star jealous, and caused frequent kicking matches between her and Nita.
Now after three years we can put the four of them together some of the time. But never at feeding time. Then it is two by two. Star and Jack in one pen, Nita and Sonny in another, and the little guys in their pen. It may make life a bit more difficult, but is better than having horses fighting with each other.