Do male cats mate with their siblings?

Yes, male cats do sometimes mate with their siblings. They are not choosy it seems. Neither are the females as they will mate with a series of males such that their litter might have different fathers. But it depends on the opportunity and the personality of the cat. 

Forgive the rudeness of the photo. Cat mating on  a car's hood (bonnet in the UK).
Photo: in the public domain.

Male domestic cats are often neutered as are female cats. And male cats arrive to mate with a female in heat and then disappear as they are solitary animals. Except when they are forced to live cheek by jowl for example in a rescue setting where many cats live in the same home of perhaps a cat rescuer who has turned into a hoarder.

I remember seeing a photograph of about fifty white cats in one home. Clearly the parents had procreated and the male had mated with some of the offspring on a regular basis to create this huge colony of lookalike cats stuffed into the tiny kitchen looking for their dinner.

And there is that well-known picture of a Japanese island famous for its cat colony. There are hundreds of ginger tabbies or that is the impression. They family has inbred for donkey's years to create this massive family of orgiastic felines going at it from one year to the next.

Japanese island colony of look alike ginger tabby cats. Photo: public domain.

The thing is you don't read about it in the books on cats. It seems that the top writers on cats don't like to write about it.

Notwithstanding the apparent reluctance to write about cat orgies, Dr Desmond Morris in his book Catwatching states that a single breeding pair of domestic cats can procreate their way to a staggering 65,000 cats in five years, at least in theory because many die. The calculation is based on the presumption that males and females are born in equal numbers and that they all start breeding when they are a year old.

Kittens can grow into unneutered adults who are content to mate with their mothers. The males desire to mate due to their testosterone is not concerned with the finer points of life. Their mother is another female to mate with. A friend of mine tried to get his male white Persian to mate with his mother. The male was entirely disinterested. Is that a personality trait issue?