Male Baldness Info

is the onset age of male pattern balldnesss determined by genetics?
for example, every guy in my family hasnt started balding till their late 30s early 40 with no early balding or premature balding.
i am 18. does this mean that i dont have to worry about male pattern baldnesss until my late 30s

can a man go bald in their 20s even though every male in their family startiing going bald in their 50s