Those two definitely Unless their kids decide that they don't want to play tennis... I don't think Steffi and Andre would FORCE their kids to play.
Kim Clijsters's baby would be Awesomely good at it with all the physical attributes (height from father, mom's legs).
Actually I don't think it's a given that the Graf-Agassi kids will be good athletes or players. Talent like theirs is quite rare, and I'm not convinced that it is indeed passed from one generation to the next.
Best left-right combination by a German (and that includes Max Schmeling): Steffi Graf. All she did in 1987 was knock Navratilova out of #1 and try to knock Evert out of the sport. (Mike Lupica in "The Best and Worst of Tennis in 1987", World Tennis)
"A couple of years ago, we nicknamed Steffi Graf's forehand 'Jaws'. And that music would go perfectly when she starts running in to the net, swarming on that little ball." (JoAnne Russell, during the 1988 Wimbledon final between Graf and Navratilova)
none. it's rare that a sports star's child is ever as good as the parent.
2 exceptions were in baseball, where (even without the juice) Barry Bonds would have accomplished more than his late father Bobby (himself a big star) and Ken Griffey, Jr. outshone his Dad, a good player.
I think players like Sharapova, Williams sisters would rather have their children doing other things beside sport whereas a mediocre player who never won a slam (who still won one or two minor titles) would press their own dreams on their children.