"My father works with you."
Translation:Tatăl meu lucrează cu voi.
"tu" and "tine" are two different species of the familiar version of "you" in Romanian. The same way how in Spanish, you would say "contigo" instead of "con tú"
When a pronoun has a preposition before it it's in the accusative case. Tu in accusative case is (preposition) tine. Same goes for eu. It will be (preposition) mine