不加。family作“家人”时表示复数概念，作主语时，谓动用复数；family一词不用复数形式。family作“家庭”时，表示家庭这个整体，是单数概念。作主语时，谓动用单数；family作“家庭”时，有复数形式，families表示几个家庭。

family的用法

family的意思是“家庭，家庭成员”，与居住的房子无关。

family作整体概念的“家庭”讲时是单数；作“家庭成员”讲时是复数。

例如: Bob has a big family.

鲍勃有一个大家庭。（family做“家庭”讲）

My family are very well.

我的家人都很好。（family做“家人”讲）

There's room in there for a family of five.

那儿能住得下一家5口。（family做“家庭”讲）

Does he have any family?

他有什么家人吗？（family做“家人”讲）

family的例句

His family have been a very positive influence on him.

他的家庭对他有十分良好的影响。

Families will be better off under the new law.

新法律会使家庭经济宽裕一些。

I always think of you as one of the family.

我一直把你当成自家人。

We think of you as one of the family.

我们把你看作家中的一员。

Their family has always been well thought of around here.

他们家在这一带一直颇受敬重。