"Non sa niente della tua famiglia."

Translation: She does not know anything about your family.

[Quazar]

So if this sentence was for "She" thats because "sa" ends in A?

[dnovinc]

No, "sa" doesn't change whether the subject is lui/lei/Lei (he/she/you (formal))

Since there is no subject pronoun this sentence could be translated as "He/She does not know anything about your family" .

Additionally I don't think it could be translated as "You do not know anything about your family. " because for that to work the Italian sentence should be: "Non sa niente della Sua famiglia"

[Martin135869]

No, it could also be a "he" sentence

[Materfamilias]

As the subject is unknown, I put " Nothing is known about your family" but I lost my heart..........

[jcool3]

How would say he does not know anything about your family.

[acqualinda]

It would be exactly the same : non sa niente della tua famiglia.