I think two things can be true at the same time, i.e. Hunter wanted to help himself
and help Sterling. It's arguable that helping Sterling serves Hunter's goals in the short
and long terms: the short being that Sterling can break the incest taboo more easily than Hunter since he's more attractive, and once broken it might become easier for Hunter to get laid also; the long being the often mentioned Dio del Sesso legacy, which I still think Hunter cares about.
Another factor we might be forgetting is that Hunter is also using Sterling as a performer for the dark web sex streams, which are immensely profitable. That's yet another way in which helping Sterling is also Hunter helping himself.