Question

The Simmons not/be a very common family​

Answer 1

The Simmons are not a very common family.

The Simmons aren't a very common family.

<The Simmons> trabaja como "they" por lo que lleva "are" ( verbo to be )

I ⇒ am

you, we, they ⇒ are

he, she, it ⇒ is