Can brother and sister cats have kittens?

Cats are animals that run on pure instinct.  In your cat’s life, one of the biggest drives they will ever have is their need to make kittens.  When breeding, the season comes along, and your sibling boy and girl kittens are both not yet neutered, they’re bound to have sex with each other and eventually have kittens together.

Our cats don’t really care if the one they’re mating with a family member. They didn’t grow up being discouraged to copulate with their brothers or sisters. There is no such thing as incest taboo for cats. Once they hit sexual maturity, everyone is fair game. 

Once the sexual hormones kick in, they’ll only have one goal in mind – and that goal is to pass on their genes to the next generation. 

Brother and sister cats can make kittens together

Unfortunately, when brothers and sister cats have sex, there is a chance of an inbred pregnancy. Breeders have traditionally bred closely related cats to make sure the kittens they produce don’t give them any surprises when it comes to how they look. 


Wet or dry cat food Quiz. What should you buy?

Breeding cats from the same litter will make the road to a pedigree cat easier for breeders.  Good breeders know which cat to choose to produce a healthy kitten.  However, there are a lot of risks involved when it comes to inbreeding – even for skilled breeders, but most especially for the accidental ones.

When very closely related cats (for example brother and sister, mother or son, or even half-siblings) mate, the risk of genetic defects increases: inbred cats are more likely to have immune deficiencies, congenital abnormalities, and have inherited diseases. 

For animals, including cats, how effective their immune system is dependent on their genetic diversity.  Cats born from parents who are genetically very similar have less ability to fight diseases – even those that usually have little to no effect on a normal cat. 

This is why, as much as possible it is highly advised that cats don’t copulate with their siblings.

Thankfully for accidental inbreeding between cats, hope is not lost. Generally, for cat siblings, depending on how they were conceived in the first place, could be pretty genetically different. Most kittens, especially those born from strays usually have different fathers. Having multiple father’s per litter is actually fairly common in cats. 

Sometimes, even kittens who have the same parents cave inherited random gene combinations – unless, of course, if they were identical twins.  If your cats are healthy – meaning there are no genetic defects present, then there really isn’t much to worry about.

The best preventive measure for inbreeding is sterilization. If you don’t want your sibling kitties to make kittens of their own together, it’s highly recommended that you have them spayed/neutered.  Cats often times come of age unexpectedly. Some reaching sexual maturity as early as 4 months old.

If you already have an inbred kitten, it is imperative that you sterilize them as early as possible so you completely eliminate genetic problems from entering the gene pool.

What are the bad signs of an inbred cat?

Most breeders, especially the less reputable ones, resort to inbreeding their cats so the perceived quality most desirable from the specific breed comes through significantly.  However, there are a lot of bad genetic faults, described as “inbreeding depression”, a term of general weakness, that can come from inbreeding.

Here are some of the things to look out for:

  • Asymmetry of the face
  • Crooked noses
  • Uneven eye sizes
  • Misaligned eyes
  • Misaligned jaws

My cat has an inbred pregnancy.  What do I do?

First off, it is important to consider the history and ancestry of the parent cats.  Do they have a history of being inbred?  Do they have genetic issues they you’re worried may be passed down to their offspring? If no, then there really isn’t much to worry about.  Unless deformity runs in the family, the kittens will most likely be born normal.

However, if you answered yes to the above questions, there’s one more thing to consider – getting your pregnant cat spayed.  If it still early in the pregnancy, your cat can get sterilized.  It is important to know that spaying a pregnant cat will result in an abortion.  Please talk to your vet if you are considering this option.

When will cats reach their sexual maturity?

Puberty for cats will vary from kitten to kitten.  There are many things that can influence how early or how late your cat will become sexually mature such as their breed and their environment. Outdoor cats, and breeds like Siamese cats will start their puberty as early as 4 months of age, while other cats can wait till their 10th month to a year to start showing signs. 

To prevent pregnancy, vets recommend spaying cats on their 5th or 6th month.  If you are very worried about having a pregnant cat, consult your local vet about getting them spayed on the 4th month – but take heed that it is safer to neuter older cats.

Inbreeding cats, especially if you are not a licensed breeder, is not the best idea as it can cause a lot of genetic problems for your cat.  If such thing happened accidentally, there is not much need to be worried – unless if the cats had signs of genetic issues. To prevent unwanted cat pregnancies, please get your cat neutered as early as possible.

Can brother and sister cats have kittens