You don't understand genetics very well do you? Hitting that genetic lottery is much more likely when they are pulling from the same gene pool than not. This is why you tend to see lots of relatives of professional players have relatives, even more distant relatives, who are also professional athletes, like NBA, MLB, NFL, etc. So and so has a cousin who is a professional baseball player or hockey player or whatever. Pulling random sets of genes from non-athlete gene pools are far less likely to generate elite genetics than pulling from the same or a related gene pool. Add into that aspect the fact that most families with elite athletes generally are more affluent and able to provide the key development needs of a budding pro athlete, and then the professional connections (the nepotism argument) as the icing on the cake, and it is a wonder we don't see more sports-dominating families, tbh.
