There is nothing bizarre in the fact that every species of animal[fish, amphibians, reptiles, birds, insects and mammals] has members that are [for want of a better term] 'homosexual'.  This IS the resulting conclusion of many biologists studying thousands of species from around the world.  

Humans also belong to the 'animal' kingdom and are born this way.  Humans don't select their mates the way animals do.  FEELINGS are strongly involved.
But they also involve biological influence.  Many biologists/medical scientists believe that enzymes transferred from one parent or another to the embryo begin the process.

It was the book of Bruce Bagemihl BIILOGICAL EXUBERANCE: ANIMAL HOMOSEXUALITY AND NATURAL DIVERSITY, utilized as evidence in court, that won a landmark case for a gay couple in Texas "Lawrence vs. Texas".