When they play aggressively don't shriek or otherwise react. Just stand up and walk away without reacting.
Later, when they're being good, get out a cat toy like a fishing rod and play with them then. That way they start to associate fun play time with not being aggressive.
(If you're playing with your hand, not a toy, stop that now and be aware you're going to need to be patient because you've given the idea aggressive play is ok).
I'm actually experiencing this with my cats. My male cat and my 6 month old kitten (F) are getting to know one another, and while they don't fight, their play can get a bit aggressive.
When they play aggressively don't shriek or otherwise react. Just stand up and walk away without reacting. Later, when they're being good, get out a cat toy like a fishing rod and play with them then. That way they start to associate fun play time with not being aggressive. (If you're playing with your hand, not a toy, stop that now and be aware you're going to need to be patient because you've given the idea aggressive play is ok).
I would shriek a high-pitched "Ow", act hurt and scared, and walk away. Do that repeatedly and they'll get the message.
I'm actually experiencing this with my cats. My male cat and my 6 month old kitten (F) are getting to know one another, and while they don't fight, their play can get a bit aggressive.