I've never been kicked in the balls but I've been punched in the balls and I've certainly done my fair share of kicking people in the balls i.e. my older brother, but then he has 6 years on me and when I was a kid he used to terrorize me constantly, Chinese burns, wedgies, cow bites, tickling me until it hurt in the "not fun" way, beating me up, strangling me Death Vader style i.e with 1 hand, holding my head in a sink full of water etc.
So yeah my only defenses were running, yelling an exaggerated "OW!" whenever he came anywhere near me and when our mum was in, in which case he'd get told off, or if our parents were out and he was being particularly evil I'd kick him in the balls in which case he'd drop like a sack of potatoes, but hey I was 5 and he was 11.... Of course one time he managed to grab hold of my leg whilst he was crying on the floor, and then manged to wrestle me to the ground before punching me in the balls; it hurt but being 5 it wasn't so bad and would probably have been way worse had I been older. Yeah he was an evil big brother all the way up until I was old enough to fight back properly.