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.