do cats mate with their siblings?
Questions About Cats

Do Cats Mate with Their Own Siblings?

Cat siblings spend a lot of time with each other in their early years as littermates and faithful companions. However, if they are not neutered or spayed before they reach 6 months old, closely related cats will begin to mate. Not only is this a difficult concept for humans to accept, but it can lead to a range of genetic problems. 

Cats don’t understand the taboos surrounding incest. Cat siblings may mate as they reach their reproductive stages. To prevent this from happening, ensure cats are neutered or spayed before they are 6 months old. If you are a cat breeder who is aiming to breed cats from the same litter, line breeding or inbreeding is not recommended unless you are extremely familiar with the lines behind your cats. 

Why cats mate with their siblings is something many cat owners are perplexed by. But, when you understand the psychology behind it, it’s not that complicated at all. The real question is what happens when sibling cats do mate, as this is where things start to become a little complicated.

Do Cats Mate with Their Siblings?

It’s possible for brother and sister cats to mate. This is because cats cannot comprehend what incest means as humans do. 

Like all mammals, mating is an instinct for cats. When a female goes into the estrus cycle (also known as going into heat), a male cat will follow its instinct to pass on its genes. A cat’s body chemistry will tell it when to mate and when it’s the right time for female cats to reproduce. Because of these instincts, cats will mate even if they’re from the same litter.

can brother and sister cats have kittens?

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 distant relatives. 

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

Can Brother and Sister Cats Have Kittens?

Did you know that kittens can be sexually mature as early as four months old? Female kittens can conceive from around this age, while male kittens can impregnate a fertile female. This is potentially bad news if you have two cats from the same litter that have not been neutered.

If a female kitten becomes impregnated at four 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 approximately 63 days. Amongst experts, this is considered far too young for a cat to be producing its first litter.

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

To prevent sibling inbreeding, it’s best to get both brother and sister cats neutered before they reach puberty. Or if you’re looking for a couple of cats to become loving pets in your home, 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’. 

Specifically, 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 lead to serious 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 helps to produce kittens than 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 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 big risk though, and there’s usually no way of knowing whether health issues will occur until the litter is born. 

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 top dollar when selling the cats as pets. 

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, simply because they are related. This can prove very 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 and time again with some of the more pedigree cat breeds. In a Scientific Reports study, 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 in human society, so many critics have issues with manipulating nature to achieve the desired result.

what happens if cats from the same litter mate?

Inbred Cat Symptoms

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

Cat breeders often use inbreeding as a way to predict how their kittens will look – particularly in pedigree cat breeds. Inbreeding helps breeders keep track of their cats’ prestigious bloodlines while fixing what are seen as bad traits. They can also promise certain characteristics to potential 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 suffer from an array of various health issues. 

Genetic Defects

Inbreeding increases the risk of genetic defects. Though more likely to appear 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, potential 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 requirements. 


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

Classic overbreeding symptoms include small litter sizes that include only one or two 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 serious health issues can occur too. 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 scary 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 vigour while reducing the rate of genetic decline. The benefit for the breeder is that they can predict the litter’s characteristics and appearance before the kittens are even born. 

If you’re choosing to intentionally breed sibling cats, or cats from the same litter, do so with caution. Inbreeding is never a guaranteed process – it’s key you understand the risks beforehand.