The explanation and sample appear incorrect.

Hola Ron

In Spanish the word "familia" is always used in singular. In English you can sometimes use it in the plural "family are..." - it depends on how you consider the word "family", you can see it as a single entity or as individuals within the group. In American English it is more common to use it as a single entity. 

However in Spanish we always use it in singular, hence "está" in that sentence that you highlighted.

I hope it clarified it.

Saludos cordiales

Inma