Genetics do play a role, but like everything else, they respond to training and can become much better.
Here's my routine that got me the best results. My calves went from 16" to 20" using this approach over time with no drugs.
Heavy standing calf raises 3x 8-10
Heavy seated 3x8-10
Free standing raises (only bodyweight) off a platform done this way:
7 reps toes in
7 reps toes out
7 reps toes forward
That equals one set. This will hurt like hell. Keep moving even if you can't get full reps to start but remember that full reps are your goal here. Also work up to 12 reps per position, and three sets. Calves respond to both heavy and volume work, and this routine delivers both.
Finish off with reverse raises off the same platform. With you heels on the platform lower your toes, and come back up for full flex. This is for the muscle that covers the shin. 2x10.
Your lower legs will grow significantly with this routine unless you only weigh 100 pounds or so (guys.) Then I would suggest a weight vest for the freestyle work.