Brian somehow managed to get his thoughts coherent enough to call out for help - and by some form of luck, though not Brian's - the man of steel happened to be flying a patrol near enough to hear it.
He came crashing into the building and when Brian saw him he felt a moment of relief, before his sister laughed.
"You think he'll save you? I have the power of all things female."
Sharon cast her eyes on Superman and licked her lips, then arched her eyebrows and before Brian's eyes the man of tomorrow popped a massive erection and collapsed onto his knees, barely able to remain conscious as his body was wracked with orgasms.
"No one can resist me, Brian - not even for an instant. Oh, but don't feel bad that you didn't realise that, it's not like could have helped you anyway. Ignoring the fact that I now wield almost immeasurable magical power, one of his weaknesses - and that my beauty is so great all mortals collapse into quivering lust at the sight of me..."
Sharon seductively strolled over to the kneeling superhero and took his hand gently in hers, then with hardly a sign of effort crushed it - inflicting incredible pain upon Superman, but because of her proximity all he could experience was lust.
"Even that gives him too much credit.", Sharon said, raising Superman to his feet and putting his arm between her breasts, she inhaled slightly and the force of her breasts pressing together crushed his arm completely.
"But, before I kill him, my interaction with you has given me a wonderful idea. While his powers are negligible in his body, his super strength in my body would make me millions of times more powerful. Superman, I want you to focus on your power - everything that makes you more than human. I want you to imagine all that power gathering in your balls, infusing your semen."
"His power doesn't work that way, it won't work.", Brian managed to croak out.
"Oh, I think you'll find men's bodies work however I want them to. Just your powers sweetie, none of your weaknesses, keep those."
"You can't do this to Superman", Brian pleaded.
"There is nothing I can't do - and I'm getting tired of explaining this to you. Time for you to take a nap.", Sharon replied before pursing her lips as if to blow him a kiss and then biting her lip seductively. Brian orgasmed into unconsciousness.
When he came to his sister was riding Superman and coaxing him on. "That's it baby, all your power, all your strength, give it to me. You know you want to. Cum."
Although the instruction was meant for Superman, Brian found himself unable to resist it himself, coming again and watching his sister coax every last drop of semen from Superman as her body began to glow with the brilliance of the sun he found himself having to look away.
When he could look again, Sharon was floating off the ground flexing her muscles. "Even I never imagined I could have such power. And the intellect, his super genius has unlocked for me so many secrets of the universe. It feels like there's nothing I can't do - but I still want more. And you, my brother, will get to watch the next step in my rise to limitless power."