he is father

tom and nancy's

他是汤姆和南西的爸爸

如果用tom's and nancy's
就要这样表达:They are tom's and nancy's fathers.

前面那个

He is (Tom and Nancy)'s father.
他是这两个人的父亲

两个人公共的在末尾的人名字加's就行拉,即Tom and Nancy's
He is Tom and Nancy's father.他是汤姆和南西的爸爸