You are attempting to produce a first conditional sentence. The clause with "if" uses a verb in the present simple tense, which for "to be", means either am, is or are. In this case, "you are". e.g. If you help me, I will give you chocolate.
Your sentence feels odd and the meaning is a little unclear. I think you are talking more about theoretical logic (and not a specific situation), in which case a zero conditional sentence would be appropriate e.g.
"If you are not my father, then no one is".