A 4 month old jenny was brought into an established herd of 5 minis (geldings and mares). There was trouble integrating her into the mix for about 6 months and we had to keep her separate, with gradual time spent with specific ones who tolerated her better than others. Two of them chased hard to hurt her and they were the last to get integrated. It was a pecking order issue and she was greatly out-weighed. Donkeys and horses speak a different language, but she has learned "horse", and now they are well integrated. She is the youngest by 10 years, but has one gelding that she plays rough with (and he plays back). I had always heard that donkeys should be in pairs. She can be loud in her braying. Also, she will go after anything small, like cats, roosters, dogs, so be aware of that. She is very sweet, and very people oriented. She is stubborn. I prefer horses actually. You need a farrier who knows how to file donkey hooves correctly as their orientation is more upright.
What do you want to do with your minis?