Do cats mate with their siblings?

Do cats mate with their siblings

It is important to remember, that cats are very different from humans, and thus, they don’t have the same sexual morals as we do.  When they go in heat, their animalistic instincts take over and they will copulate with whomever is available.  This is why, if you have a brother and sister cat living together and neither of them are spayed, they are bound to mate with each other.

However, that doesn’t mean that sibling cats should breed with each other.

The advantages and disadvantages of inbreeding cats

Believe it or not, there’s actually an advantage when it comes to inbreeding cats.  Breeders inbreed their cats for predictability and to eliminate unwanted traits.  However, when not done properly, it could cause a lot of problems.  Through inbreeding, the strengths are doubled, but so are the weaknesses.

Cats who mate with other cats who have very similar DNA to them are at risk of having kittens that have a lot of genetic defects.  This is true for both pedigree and nonpedigree cats, although the former is known to get it more often.

Inbred cats who are overbred are prone to having smaller litter sizes, have deformities like crooked noses and jaws, and even abnormally sized eyes that could be different from each other.  They’ll also have weaker immune systems and be more prone to get cancer which could lead to early deaths.

What do I do if my cat accidentally mated with their siblings?

In most cases, this is not something you should worry about too much – especially if your cat is not a pedigree cat.  If your cats were once strays or were the son and daughter of a stray, chances are they probably have different fathers.  In the wild, one cat pregnancy has multiple fathers.  Your cats’ DNA could be different enough from each other that their kittens would be okay.  Just know that you MUST spay and neuter all of the kittens as to not pass along bad genes to the next generation.

If you are unsure or unable to take care of the kittens that are bound to come your way, you can get your pregnant cat spayed.  Getting a pregnant cat neutered will terminate her pregnancy.  You may need a bit of time to think about this.  Please consult your vet.

Here’s some things to help you decide if you should push through with spaying your pregnant cat:

  1. If it’s too late into her pregnancy, it is not advisable to terminate the pregnancy.  If you don’t know how long your cat has been pregnant, please let your vet estimate the term for you.
  2. Very young or very old cats will have more potential problems with delivering their babies.  Please make sure that you cat is at their best health while they’re pregnant and after.
  3. Ask everyone in your household and asses if you are able to take care of the newborn kittens when they arrive.  Kittens require a lot of attention, time, patience and money to keep them healthy and happy.  Make sure that everyone is on board.  If you’re unable to take care of the kittens and it’s too late to get your cat spayed, please turn them over to your nearest rescue organization.

How can I prevent inbreeding?

The best way to prevent inbreeding, or any form of unwanted cat pregnancy, the best course of action is to get your cats spayed and neutered.  Even if your cats are not siblings, it is best to keep them fixed early as to not have accidents.  Cats become sexually mature between their 4th and 12th month of age, so it’s best to get this done as early as possible.


Common questions about cat breeding

How to tell if cats are siblings?

Generally, cats born from the same litter could be very different genetically.  That’s because, unless the breeding happened in a controlled setting, one litter could have different cat dads.  Even if they have the same pair of parents, it’s still possible that the kittens have inherited random sets of genes from their parents.

The only way that two cats can have the exact same of genes is if they were identical twins.  Other than knowing that your cats are from the same litter, the best way to know how similar your cats are to each other is to get them through DNA testing.

What is line breeding in cats?

Line breeding is a milder form of inbreeding.  It’s when a breeder chooses to breed related cats that are not very closely related, for example a grandparent cat and a grandchild cat.  This practice is seen as a safer way to keep the pedigree of the cats, although when done irresponsibly, it could still have the same effects as a closer inbreeding.

Do cats mate with their parents?

If an intact male is around an intact female during the in-heat season, chances are they will mate with each other.  It doesn’t matter if they are brothers and sisters, cousins, or parents and offspring.  When they’re in heat, cat’s sexual impulses will take over, and it really doesn’t matter to them if they’re doing it with mom.

To avoid this, please get your cats spayed and neutered before they turn 6 months old.


For us humans, it is severely understating it to say that inbreeding is looked down upon.  For cats, however, it’s a different story.  Cats simply don’t think the way humans do.  If your cats accidentally inbreed with each other, most of the time, it’s nothing to worry about.  As a preventative measure, please spay and neuter your pets as early as possible.

Do cats mate with their siblings

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