Fixed kittens attempting to mate?

I have two new kittens (one I have adopted and the other I am fostering). One is male and the other is female. Both have been fixed (very recently about a wk and a half ago) but they seem to be attempting to mate! Could they hurt themselves? I mean they did just have surgery. Also I have a 1.5yr old male cat who is also fixed, should I be worried about him attemtping to mate with her? I'm quite confused because they are also only about 4 mths and I thought that kittens didn't reach sexual maturity until about 6 mths. Any insight would be helpful.

Nope cats can reach maturity as young as 4 months, that is why it is suggest to spay and neuter immediately, can be done a 2lb or about 7weeks, but well before 5 months of age. Anywoo, it could be a domiinence thing. Cats will have to establish who is alpha in the house and will do that my humping, it isn't a sexual thing, but just for dominence. I would think they are too young to be doing this though.

What I think it is, is that your male is sexually mature and if he was just neutered a week ago. Sperm and hormones don't leave the males system for about a month after being neutered. So he can still impregnate females for about another 3 weeks. Luckily your female is spayed so you don't have to worry, but do not let him outside yet if you plan to at all.

For now, if it is an ongoing thing I would seperate him for awhile until the month is up and he will stop harassing her. Maybe crate him when you aren't around or put him in the bathroom. You don't want to freak her out especially with a wound on ehr belly that is still healing.

It's nothing to worry about. It's not really an attempt to mate, more of play/dominance thingy. My Ichi used to mount his brothers and sisters at 4 mos. I thought he had some kind of behavior disorder .
Yes, they reach sexual maturity around 6 mos. (at least in my experience).The only cases I've heard when the cat acts up like she's in heat is when the surgery was badly or incompletely done.