I'm sure to be ignored or contradicted , but my Greek tortoises, all related, have been together since they were hatched . going on for 20 years. They don't fight each other, males do get rambunctious when they fall for a female, even then they aren't promiscuous. Blackie is in love with Reeva, Dana only has the attention of George. It maybe because they are just used to each other, or it could be the species . Every morning when I lift off their house, the adults are all huddled together, except for Blackie who is usually on patrol. All 25 are doing well , babies getting stronger by day, plastrons nice & firm. If there are a lot more babies next year I shall lengthen their enclosure.
Groups usually do fine. Larger groups like yours usually work even better assuming they have enough space. PAIRS are the problem we are advising against here. Pairs are almost always a problem.