I have three cats - an almost 4 year old (altered) male - and two litter mates almost 2, a male and a female (altered). The kittens arrived when the older one was almost 2 years old (they were 6 weeks), and he quickly became the "parent" cat to the two kittens. When the kittens were old enough - about 5 months - I slowly began letting the older one have more contact without as much supervision.
KiKi - the older one - rather enjoyed playing with the little girl - she seems to fascinate him, especially if she's busy playing.
Phoebe is very vocal about her "play" - she growls and hisses - but he is undaunted about the growling and keeps "attacking" her. She's found places to get into where he cannot get to her. She "fights" differently than the little boy, which I think makes her more vulnerable for KiKi to "pen" her. Sometimes she's a little stinker to KiKi - so she deserves what she gets.
Simon holds his own with KiKi, and I don't watch their play as much.
But, when Phoebe and KiKi get into "it", I pay attention. When things start getting rough, I break them up. If they persist, I put one - usually KiKi - into a room for a few minutes "time out", that usually does it.
Two nights ago, after I had gotten into bed, they started playing - loudly - I didn't have any patience to just let them "go at it", and listen to the growling, knowing that KiKi had her penned somewhere, so, I got up, went to where they were, KiKi knew he was in trouble and immediately ran off. I picked up Phoebe and took her into the bedroom with me and closed the door. It wasn't until I got up later, in the middle of night, for a "bathroom break" that I opened the door - by then KiKi's interest of play was gone - so the remainder of the night was quiet.
My point, I guess, is - I don't let them actually fight - I can't take it.
. Some play is good, but when I think things are beginning to get serious, I break it up.
I don't like seeing children hitting each other, and I don't like the Furbabies hurting each other - so, I try to keep things more peaceful around the house. Oh, by-th'-way - sure saves the house from getting all wrecked.