Homosexuality and its anthropomorphized connotations of sex and love are easily projected onto other animal species. Juvenile male lions will copulate as a form of bonding as they search for females to establish their own pride with, and dolphins are notoriously bisexual.
But for the concept of being nonbinary, it is distinctly harder to conceptualize.
The great cycle of life and its endgame is to have sex and to procreate, which is then dependent on sexual organs. The idea of rejecting an identity dependent on the existence of our dichotomous biological sex as humans is so radically antithetical to the great race of life, evolution, and genetics.