Let us start with data from identical twins:
Take wrestling. Of 6,778 Olympic wrestling athletes, there have been something like thirteen pairs of identical twins. This implied that the identical twin of an Olympic wrestler has a better than 60 percent chance of becoming an Olympic wrestler himself.
That is from the forthcoming Seth Stephens-Davidowitz Don’t Trust Your Gut: Using Data to Get What You Really Want in Life. From such reasoning you can divine the relative import of genetic factors for success in various sports. Here are the derived calculations, with the number indicating “Percent of Same-Sex Siblings Who Are Identical Twins” (when both make the Olympics, or achieve some other status):
Track and field: 22.4%
NBA players: 11.5%
NFL players: 3.2%
MLB players: 1.9%
Alpine skiers: 1.7%
Divers, equestrian riders, and weightlifters: All zero percent.