The right conjugation is tienes. So:
Tú tienes una familia grande (You have a large family)
This sentence is given in the present tense. In Spanish, the simple present tense (el presente or el presente de indicativo) is used to talk about habitual actions, routines, things happening now or in the near future, universal truths, facts, hypotheticals, lapses of time, and for ordering in restaurants and stores. There are both regular and irregular indicative forms.
This sentence is an universal truth, that is, the family of that person is large. The verb tener is irregular, so the conjugation of this verb for the second-person singular is tienes.
