Younger cat bullies older cat

Alright, to make this short. About a year ago, I adopted two 2 week old kittens. They are now 11 1/2 months old. OK, however, I also have a 6 year old cat that I had way before the kittens. My older cat is timid and basically only trusts me and my mom. She delt with the 2 new babies alright. She basically just tolerated them as much as possible. They kinda of kept their distances for a while. But lately, one of the kittens "Diego" Playfully attacks my older cat "Chloe". He never hurts her, he just likes to sneak up on her and jump on her and roll around with her. I can tell she is annoyed and frustrated with him. I hate when he does that, but also in a mean sense of the way, it is a bit funny. Sometimes she will hiss or put her paw up, but that is about it. But Diego has a twin brother who he always plays with, he only jumps on Chloe when he is being playful and wild with his brother and Chloe just happens to be in the way. My question is how do I get him to stop and what is the best way to disipline him. Thanks.

If there is no bloodshed, I would try to let them work it out amongst themselves. I have the opposite problem--my new cat was older than my resident, and he picks on her at times. She'll tell him when she's had enough. I also provide places where she can go that he either can't or won't (in her case, furniture she can jump up on to get away from him). I figure I can't be around all the time to supervise, so it's best if she can give the signal to stop him from swiping at her.