Everyone always thinks of brothers when they think of siblings competing athletically, but boy-oh-boy, do sisters love to compete, too. If there was nothing you and your sister loved more than a good foot race when you were kids, then you might think of branching out to some more esoteric sports. You might consider giving your athletically competitive sister a badminton kit so the two of you can smash that birdie back and forth without fear of injury. Or you might try the more refined games of c...more