Can a male kitten be sexually mature at the age of 4 months?

No, male kittens are slower to mature than females and are generally ready to mate between 9-10 months old. Females can go into estrus as early as 6 months but most females are ready between 7-10 months old

From an accurate website:

"* The testes of males may become visible as early as 4 weeks of age. In domestic cats, males reach full sexual maturity, if they remain unaltered, between 9 and 12 months of age.

* Most females reach sexual maturity at around 10 months of age, although instances of much earlier pregnancies have been recorded."

http://www.kittens-lair.net/cat-mating-and-pregnan...

(Have to laugh reading some of these answers. The difference between the advice of an experienced breeder or the advice of an experienced answerer with NO experience in breeding! LOL Most of the people who answer these questions have never even raised a kitten to breeding age, let alone even bred ONE litter! I've had a least 3-4 hundered kittens over the years, many I have until they are 4months old, some even 5 months and NEVER have I had a male or female able to mate and breed kittens at that age. Of course I do believe if you are not raising registered kittens it is best to spay or neuter them. BTW, most all breeders state in their contract to have them spay or neutered by 6 months old. Now if we had to worry about kittens having kittens we all would change the age, but in reality we don't because we really do know better, Au Contraire to the uneducated advice given in these forums) *wink*

It is extremely unlikely though theoretically possible.

It would be better, and easier on them if you got her spayed and him neutered now. Kittens can be spayed or neutered much younger than 6 months of age. When they are, they recover and heal very quickly.

Some clinics will neuter males at 8 weeks/2 pounds and females at 10 weeks/2.5 pounds. Nearly any vet or spay/neuter program will do the surgery long before 6 months.

The last time I spoke with a vet about this issue he said that in his experience most male kittens were at least 8-10 months old before beginning puberty. Vets can tell by looking at the development of spines on a kitten's penis (yes, adult cat penises have spines).

Play it safe and get it done as soon as you can so you don't have to worry and wonder.

Yes - both male and female kittens are capable of breeding. This is why I said you need to get an emergency spay for the female, and then neuter the brother. Do not wait. At her age, she can easily die trying to give birth or carry kittens inside her. And she will have no idea of how to care for them if she manages to live - those babies will probably die at a very young age.

Don't believe the "sexually mature" age - there are far too many mommy and daddy cats at 4 or 5 months old to think its a reliable "I don't have to worry about them".

Short answer, yes he can. 6 to 8 months is a general guide for full sexual maturity. Puberty, however, starts earlier and he could be capable of impregnating his sister even if other signs of sexual maturity have not shown up yet.

All your cats need to be fixed ASAP. You can check the ASPCA's website for places that will do it for low or no cost. (It's often free if you are on food stamps or unemployment or something, low cost for everyone else. I got my cats fixed for $20 each when I was strapped for money.)

No he can not. He is too young. I have a book on breeding and it says they are ready at around ten months old.