Pointing out your shared kinship with someone gives you the chance to win over creatures associated with your bloodline.
Benefit: When attempting a Diplomacy check to influence a creature with a plausible connection to your sorcerous bloodline, you may instead make a Bluff check. For example, a gnome sorcerer with the draconic bloodline may use this feat against dragons and their kin, but no other creatures.
Pathfinder Companion: Gnomes of Golarion. Copyright 2010, Paizo Publishing, LLC; Authors: Hal Maclean, Colin McComb, Mark Moreland, Jeff Quick, Sean K Reynolds, Steven Schend, and Owen K. C. Stephens.