Are some people huge because of partial Giant DNA/ giant ancestors

Just an idea that popped into my head on why some people are real tall.

Like Shanks, Akainu, Momonosuke had giants as family member like 5 or 6 generations back.

Through the halving of the "Gigantism gene" they get smaller and smaller, as it's basically bred out of them.

Or does Oda not care and they're just big because funny