I know you can breed in faults in chickens if using related stock, but on the other hand you can use related stock to improve stock. Wondered if not showing birds, if using related ducks normal and healthy with no known problems, would it matter. I should think mating the offspring of brother and sister together, which would also be brothers and sisters, second generation, would be a bit iffy. Hope someone can follow this cause i'm getting muddled and probably having a senior moment now.