Ngl Sterling putting on this much muscle and height from just GH shows he's a freakish genetic phenom with the likes of CBum and Arnold. Agree that Drew shouldn't have reproductive capabilities tho, with how self-aware the characters are, it wouldn't fit.
Counter offer:
Drew was born intersex with a potentially functional female reproductive system and a small poorly formed clitoral penis.
Hunter insisted on raising Drew as a male and had some form of surgery and/or hormone treatments performed to help make the penis bigger and better. Thus, Drew was treated as and referred to as a boy growing up.
Once old enough to express and fight for his own opinion, Drew started "transitioning" to female, activating a functional female system. This switch would have to occur mid puberty, old enough for the "penis" to grow, but before it was too late to activate the female systems.
This could, theoretically, be possible and would mean Drew could get pregnant. However, it would also mean her penis is really just a giant clit and could not be used to impregnate anyone else. It does have to be one or the other if any level of realism is to be achieved ( at least as far as recorded case studies go).