Just another argument against AI - I'm not in favor of it even with dogs because it does the same thing that happened here -- makes a very few sires predominant in the gene pool. When you require natural cover (as the Jockey Club does with Thoroughbred horses) it limits the number of females that can be bred to any given male, but with AI (especially with modern techniques like ovulation testing and concentration) the number of pups is pretty much infinite.
It turned out that a very, very popular National Field Trial Champion who sired literally thousands of pups via AI was carrying a serious genetic defect. When he popped up in 2-3 places on a dog's pedigree, so did the defect. And for awhile there it was very hard to avoid him - people were advertising stud dogs in the magazines with "No [dog's name]".
YES...what YOU Said....how do children of this procedure who live in the same city all of their life avoid marrying a half brother or sister? I’ve often wondered that....(In the 80’s they were doing AI for single/divorced moms who just wanted a baby....I know....I have a relative who did just that.)