KIN RECOGNITION IN ANIMALS. “Many animals are able to distinguish close relatives from strangers and to act differently towards their kin. Individuals are expected to behave preferentially towards kin to increase their inclusive fitness. For example, recognition of kin allows individuals to direct altruism towards kin, avoiding the costs of behaving altruistically towards strangers.”
http://rspb.royalsocietypublishing.org/content/280/1756/20123062.short