my personal opinion is that genetics do play a large role, but lifestyle affects this as well. for instance my uncle and uncles father have enormous calves (very muscular) and enormous forearms, they are both fisherman. always using both of those muscles all the time.
my calves are horrible. but it has to do with my height, im 6'3", so to have big calves i'd have to weigh much more than I do now, probably 245+, but i have great genetics. so go figure. then again i don't do any direct calf work