We purchased a 12YO recently gelded mini a few months ago. The horses are separated at night but during the day he shares a pasture with a very laid-back 17-hand thoroughbred gelding. At first he copied everything the big guy did. He never rolled & scratched but now he does it every time the TB does. He refused coastal hay until he saw the TB eating it. Anyway, now the mini has become the boss in a bad way. They can't share the pasture because the mini won't let the TB anywhere near the water and finds reasons to bite him chronically. I know horses bite, but the vet was taken aback at the 30+ new and healing bite wounds all over this huge TB. I started rotating pasture time but the mini got very depressed being away from the TB and moped around like Eeyore. We added a Chincoteague pony mare to the mix last week. The mini leaves her alone but his relationship with the TB hasn't changed. I don't want our mini isolated and depressed but it's not fair to our very polite gentleman TB to be terrorized by this little guy. The mini is good with people. He tolerates adults and is very kind to children.