do cats mate with their siblings?
Questions About Cats

Do Cats Mate with Their Own Siblings?

Cats’ siblings spend a lot of time with each other in their early years as littermates and companions. However, if they are not neutered or spayed before reaching 6 months old, closely related cats will begin to mate with each other, leading to a range of genetic problems. 

Cats don’t understand the taboos surrounding incest. Cats’ siblings may mate as they reach their reproductive stages. To prevent this from happening, ensure that your cats are neutered or spayed before they are 6 months old. Line breeding or inbreeding is not recommended unless you are familiar with the lines behind your cats. 

Why cats mate with their siblings perplexes owners. But once you understand the psychology behind it, it’s not that complicated at all. The complex part is what actually happens when sibling cats do mate.

Do Cats Mate with Their Siblings?

Brother and sister cats do mate with each other. Like all mammals, mating is a basic instinct for cats.

When a female goes into the estrus cycle (going into heat), a male cat will follow its instinct to pass on its genes. The cat’s body chemistry will tell it when to mate and when it’s the right time for female cats to reproduce. So, cats will mate, even if they’re from the same litter.

That’s not to say that inbreeding always occurs naturally, though. A study in Brill looked into the female control of paternity during copulation. Researchers found that overall, female cats avoid inbreeding with their close kin during copulation but not with their distant relatives. 

When looking at feral cats that are isolated from other colonies, they have no choice but to breed with their siblings and other family members to keep the colony going. However, the report shows that feral cats prefer to find a mate that is not within their direct bloodline if other cats are available.

Can Brother and Sister Cats Have Kittens?

Kittens can be sexually mature as early as 4 months old. Female kittens can conceive from around this age, while male kittens can impregnate a fertile female. This can be bad news if you have 2 cats from the same litter that haven’t been neutered.

If a female kitten becomes impregnated at 4 months old, there’s every chance that the cat could produce its own litter at only 6 months old. This is because a cat’s gestation period is just 63 days. Experts believe that this is far too young for a cat to be producing its first litter.

Cats are also indiscriminate creatures. This means a brother may mate with his sister because he doesn’t recognize her as family. More than anything, they are playmates.

To prevent sibling inbreeding, it’s best to get brother and sister cats neutered before reaching puberty. Or, if you’re looking for a couple of cats to become household pets, you could choose same-sex cats from the same litter. That way, you’re reducing any risk of sibling mating while still providing a playmate for one another. 

Can You Breed Half-Sibling Cats?

Inbreeding between half-sibling cats is just as common, if not more so, as inbreeding between full sibling cats. In the cat breeding world, purposefully mating half-siblings is known as ‘line breeding.’ 

Line breeding involves matings between second-degree relatives (including half-siblings). The process reduces the risk of inherited disorders when compared to the mating of first-degree relatives. It doesn’t prevent the risk entirely, though. Any form of inbreeding can cause health problems.

Inbreeding of not-too closely related cats is preferred by professional breeding bodies over full-blooded mating. As described in the GCCF Breeding Policy, breeding half-siblings produce kittens that conform to a particular breed’s integrity and physical and genetic characteristics. 

What Happens If Cats from The Same Litter Mate?

If cats from the same litter do mate, there’s every chance that their kittens will be born healthy with no obvious genetic issues.

With luck, the litter produced will have all the desired physical and personality traits without any major defects. Inbreeding can be a huge risk, and there’s usually no way of knowing whether health issues will occur until the litter is born. 

can brother and sister cats have kittens?

Similar Physical Traits 

Cats born through inbreeding will often inherit certain characteristics that are specific to their breed. This may include certain physical traits that are considered attractive.

This could be the size of their legs, the absence or presence of more fur, or the shape of their skull. For cat breeders, this allows them to achieve the best prices when selling cats. 

Similar Personality Traits

It’s not just physical characteristics that an inbred cat will inherit. There are likely to be personality traits, too. This is why mating cats from the same litter is done so often by cat breeders – they can shape the temperament that the litter is born with. 

Breeding sibling cats can produce a calm temperament or a playful demeanor if the parent cats share the same personality. The likelihood is that they will because they are related. This can be attractive to owners looking for a specific type of cat to fit in with their lifestyle. 

Mate with Caution

If inbreeding is allowed to continue too often, serious health problems tend to occur time again with some of the more pedigree cat breeds.

According to Scientific Reports, 64.9% of Persian cats studied recorded at least one disorder. As Persians are one of the most inbred breeds, this high statistic begs the question: ‘is it safe for cats from the same litter to mate?’

There’s the morality of the practice to consider, too. Inbreeding isn’t socially acceptable to humans, so many critics have issues with manipulating nature to achieve the desired result.

Inbred Cat Symptoms

Inbreeding occurs when closely related cats mate. This includes brother and sister, father and daughter, mother and son, and half-siblings. 

Cat breeders often use inbreeding to predict how their kittens will look, particularly pedigree breeds. Inbreeding helps breeders keep track of their cats’ prestigious bloodlines while fixing their bad traits. They can also promise certain characteristics to buyers who are looking for something specific in a feline.

However, inbreeding is not without its problems. Not only is it seen as ethically and morally wrong, but cats born through inbreeding can experience various health issues. 

what happens if cats from the same litter mate?

Genetic Defects

Inbreeding increases the risk of genetic defects. Though more likely to occur in pedigree cats, all inbred cats are vulnerable. Inherited disorders arise due to abnormal genes that are passed down through the generations. They can be obvious at birth, while others may not develop or present themselves until later in life. 

The limited gene pool caused by continued inbreeding means that harmful genes become widespread, causing the breed to become sickly and weak. 

As a natural by-product, buyers aren’t usually willing to purchase a cat that displays obvious health issues, rendering the animal unsaleable. Breeders will often choose to put the animal to sleep because it doesn’t meet the requirements. 


Cats regularly bred with cats from the same bloodline will eventually start to produce litters with more harmful health issues. 

Classic overbreeding symptoms include small litter sizes that include only 1-2 kittens. These kittens may be born with a series of abnormalities, including a misaligned jaw, crooked nose, wonky eyes, and teeth and mouth defects. 

Other adverse issues can also occur. This includes low fertility in female cats, immune deficiencies that result in a high death rate, and cancers in infant cats. 

Maintaining Breed Purity

A less worrying outcome of inbreeding is the ability to achieve purity through line breeding.

By mating cats that have a less direct bloodline ­– for example, cousins or half-siblings – will help preserve the breed’s vigor while reducing the rate of genetic decline. The benefit to the breeder is that they can predict the litter’s characteristics and appearance before the kittens are even born. 

If you’re intentionally breeding sibling cats or cats from the same litter, you should do so with caution. Inbreeding is never a guaranteed process.