Is height mostly genetic?

I saw a lot 7 footers on the internet came from average height families. For example, 7'9" Bao Xishun came from an average height family and has a son of average height. Another one would be 6'9" Elisane Silva who also came from a average height family too. Last one, 7'7' NBA player Gheorghe Mureșan came from an average height family and has sons shorter than himself.