At the seder, a question came concerning Elihahu. He is described in Tractate Ediyot Perek 8 Mishna 7 as one who brings close those kept distant. There is an example concerning Bnai Tzion and Beit Tzrifa. Who are Bnai Tzion and what is the story with Beit Tzrifa?

Beit Tzrifa was a family, apparently wealthy and powerful, that misused their power to help their friends and hurt their enemies. They "arranged" for kosher families, that is families whose lineage was pure and could marry other Jews, to be declared "Pasul" - unfit - and for Pasul families (for instance Mamzerim) to be declared pure. Ben Tzion is the name of a kosher family that was "estranged" - declared Pasul. The Rambam explains that prophecy is not used to make halachic determinations, but in order to right this terrible injustice, Eliyahu will declare as pure families who were estranged by violent means.