I have 2 kittens. One is 6 Months and the other around 3. The 6 month is a Tom. We are going to get him neutered soon. He seems mean to animals. Is this his tomcat nature? He plays too roughly with the other so I try to keep them them apart. Will they ever get used to each other? Sometimes the male is really sweet but he has a lot of energy and can play really rough and bites hard. What should I do? Thanks!
Around this age, he is starting to experience a rise in testosterone levels, and that can certainly play a role in how quickly his aggression escalates during play. As a rule, tom cats are more competitive due to high testosterone levels. But at six months, his hormone levels are not at full force, and I don't think all his behavior is attributable to being a tom. It's not normal for toms to be mean to animals as a rule (territorial aggression notwithstanding).
Lack of social experience usually has much more to do with difficult personalities than hormones do in young cats. I would suspect your older kitten probably wasn't able to stay with his litter until the recommended age of 12 weeks. Most people believe that because a kitten can be weaned around 8 weeks, he can healthily leave his family. But he still has a lot of valuable lessons to learn about interacting properly with individuals of his own kind.
Between 8 & 12 weeks, he will learn through the feedback of his siblings (squawks, defensive bites, retreats, etc.) and through the corrective swats of mom which of his behaviors are too aggressive. He'll learn not to engage in these behaviors if he doesn't want to receive a swat or a bite and if he doesn't want to lose his playmate.
Kittens who leave their litter and mom before fully learning this lesson tend to be bullies when they're introduced to a pet in their new home, because they simply haven't learned how to interact. While bigger pets can put these cats in their place pretty quickly, smaller pets can struggle to defend themselves, so in your case, you do need to keep the two separated except when you can be there to play referee. Your older kitten can still learn to play nice, but he can only do so by interacting with your other kitty. You should separate the two as soon as he shows any sign of getting too excited.
See if you can use interactive toys between them, like ribbon and feather wands. These are good ways to get them playing together without full-on wrestling. Allow the two to play and even wrestle as long as the smaller one doesn't cry out, hiss, or try to hide. Then, it's a time out for the rough guy.
As the younger one gets bigger, (s)he'll be better able to hold his/her own, and you shouldn't have to do as much monitoring. Your older kitten should also start to get a hang of this socializing thing and begin to understand what's ok and what's not. Some cats do remain bullies, but I find it very uncommon among neuters.
If you do run into that problem, it can usually be resolved by creating more vertical space in the home, in the form of cat trees. The cats like to sit on perches. They both feel secure having claimed their own space, and they leave each other alone.