Would explain why quite a few tennis players seem to have decent calves for their body size...
I would agree that it is mostly genetic. But I have also read others have had good results with using a combination of standing and seated calf raises, 3 times a week give or take. Also, to target the left/right sides of each calf, you can alternate between pressing up with the big-toe side of the foot and the pinkie side of the foot. But apparently it's not so good to actually rotate the foot (toe-in or toe-out).