"My family is not that big."
Translation:La mia famiglia non è tanto grande.
I don't know... maybe "familia" is treated as plural because it has many members, and for plural family members articles are used?
It is not a good explanation... I am just trying to comfort myself a little.
Another attempt: "famiglia" is not a person. It is an abstract concept. So the rule "Don't use articles for family members in singular" does not apply?