Jody's late dad probably made him gay
I watched some early eps of this show on DVD recently and I saw that Burt in a struggle with Jody's deadly father killed the latter. Well, that would tend to mean Jody was pretty isolated from his biological dad and a webpage called mygenes.co.nz shows that gays are extremely often veterans of bad or non-existent parental realtionships (plus they have something called neuroplasticity)and this causes them to be gay. Danny, being much fiercer than Jody, was probably their mean father's favorite child so he presumably received more family love than Jody did (even Mary seems to be way crazier about Danny than Jody).
PS I do not know how much of this the writers intended but it is nearly impossible the writers knew about neuroplasticity back in '77.