Jeff had wanted a bit of a brother and given his little sister Emily a cock to make her a functional hermaphrodite. Jeff was unsurprised that his sister was still just as much of a girly brat despite the addition.Jeff decided to try to turn things up another notch and made Emily's cock larger than his own even at her prepubescent age.
When Jeff caught back up with Emily in the family living room she was more interestingly different. Her hair, makeup, and top were all possibly more girly than usual. That was perhaps to over compensate for the fact that she wore a very loose cut pair of boy's jeans below. Even with a very loose cut, there was a very noticeable bulge in the crotch of those jeans. Emily even brought more attention to it by bringing her hand down in a very manly readjustment of her cock's position in her jeans followed by a subtle scratching of her balls through the jean fabric with her painted nails.
Jeff wasn't the only one who noticed he was staring at his sister's crotch, and Emily giggled a very girly giggle and then followed it up with a gruff attempt at sounding masculine, "Yo, bro, what are you looking down there for, my budding tits are up here. You gay or something?" Jeff looked up to meet Emily's eyes, unsure how to respond and Emily giggled again. She said in a less teasing voice, "I'm just joshing you bro," and punched Jeff gently in the shoulder. Then Emily gently tugged her top to better emphasize her growing curves and in a high cutesy teasing voice added an, "Unless..." When Jeff continued the awkward silence, Emily broke down laughing. "You are so easy to tease, bro. Anyway, let's play some Smash."
With that Emily flopped down on to the couch, absent-mindedly manspreading her legs while doing so, and grabbed a controller. Jeff sat down to join her, also grabbing a controller. Through a set of negotiations and small dares/wagers they settled on a series of "Space Princess" battles where the only Smash Brothers characters they could choose from were Rosalina and Samus and their variations.
Deep into many rounds of Smash (and Emily beating Jeff almost 3 to 1) Jeff couldn't help but glance over at his sister and notice the long boner running down her pants leg.