My cousin, who is 44, eats like sh*t, drinks almost every night, smokes since 16 yrs old, and its 80lbs over weight, inherited my grand dads thick nw0 hair. His hair is perfect, low hair line, thick, perfect. The funny thing is he often buzz cuts it because he is too lazy to comb his hair.
Its all genetic, if you're meant to go bald you will.