I come from a nuclear family.

我来自一个小家庭。

My cousin is not part of my nuclear family.

我的堂表兄弟姊妹并不是核心家庭的一部分。

My cousin is not part of my nuclear family.

我堂兄不是我核心家庭成员。

The traditional American family is a nuclear family.

传统的美国家庭是核心家庭。

A nuclear family is somehow impregnable, beyond reproach.

从某种程度来说，一个核心家庭是坚不可摧的，是无可非议的。