If one or both parents or a relative is born deaf, there is a higher risk that a child will be born deaf.

如果父母一方或双方或某一亲属有先天性耳聋，子女得先天性耳聋比例就较高。

youdao

I think once the second son is born there will be a three or four year period before the third child.

我想一旦第二个儿子出生，那么第三个孩子就要等到3或4年后才会有。

youdao