Dating Your Mama
There's a word for that, and it isn't nice.
Purebred dog breeders will sometimes post that they need to incestuously breed dogs to "fix type".
You may ask "What was wrong with their dog's type that it got broke and needed to be fixed?"
What the dog breeder is really saying is that they want to "fixate" type - they want all the dogs to have the same look; they want the puppies to look very much the same way that the parents look.
It is common for puppies to look somewhat like their parents, but not exactly like their parents. But by breeding brother to sister, son to mother, father to daughter, the purebred dog breeders fixate a certain look into their line of dogs.
Unfortunately, inbreeding fixates not just the traits you wanted to fixate, but other traits too.
Some of these traits are INSIDE of the dog, and the puppies might look the way their breeder wanted them to look, but inside of the puppy, unhealthy inbred traits can express themselves causing health problems.