Genetics can effect beard growth. I know that so not sure about the T effects, but genetically Some Native American tribes are unable to grow facial hair, and are fairly hairless in some parts of body. Some Caucasians and mixed heritage people have spotty beard growth.
I'm hoping I don't have the spotty beard growth like my father, then again not sure if having a great great grandmother who was Chickasaw Indian on mom's side would effect anything lol *shrugs*