Dogs from the same litter are able to breed and produce living puppies. However, the close genetic relationship sometimes leads to health or physical issues in the offspring.
Breeding siblings is a form of "inbreeding," which refers to the mating of closely related dogs. When dogs within the same family are bred, the amount of genetic information is limited. Therefore, puppies are more likely to inherit genes that cause problems such as tumors, heart disease, bone disorders, immune system diseases and epilepsy. Puppies that come from unrelated parents have more genetic variation, so problematic genes are less likely to "double up" and produce defects.