A Birthright is an inherent power available to a Beast based on its Family. The Birthrights are reflective of the type of fear each Family embodies. Anakim, for instance, have the ability to smash through any structure as a Birthright.
In the Beast: The Primordial Rulebook, each Family was given single Birthright. The Beast Player's Guide presents options of alternative Birthrights for each Family, as well as the option of a Beast acquiring multiple Birthright powers as they increase their Lair.