Offer to workout with her, and test out making her bigger and stronger.

As Felicia talked about working out and getting some muscle and size herself, an idea popped into your head. You were already bigger and could grow more anytime you wanted, so why not share the wealth and change Felicia too?

"Well I think you look great, but I could workout with you if you want. Maybe show you some tips and get you growing like me," you said. The idea of changing your brother's woman only turned you on more as your eyes wandered down her body, taking their time as you imagined what you might want to change. Now that you knew the app on your phone would work, the possibilities were endless. Maybe she would look better with more muscle like she wanted, and now you could give it to her with the push of a button.

"Yeah that doesn't sound bad, plus you seem to know what you're doing and I don't have much planned today. Might as well give it a shot," she said. You felt your cock twitch as she agreed to your plan.

"Great! You should go change into something skimpier," you said, scrambling to re-word things. "I mean something more for working out ya know?"

Felicia's face was crinkled up a bit as your slip of the tongue didn't go unnoticed, but in the end she couldn't exactly workout in a full dress, so she left to go and get changed. Part of you wanted to follow and spy on her, but being caught doing something like that would definitely be foolish, so instead you whipped out your phone and switched over to Felicia's profile. As you setup some of the options, you noticed a choice for 'Voice Activated Changes' towards the bottom.

"Huh," you said, tapping the option to enable it. It gave a quick message about draining size from random contacts whenever you issued a command, not that you paid much attention to the details of the warning. Being able to make changes without having your phone out could be useful, even if you weren't sure exactly how it would work. It gave a pop up saying to start commands with a trigger phrase, with you quickly tapping through for the phrase 'I think' before continuing on. Unfortunately you heard Felicia's footsteps coming back into the living room before you could test it, sliding your phone into your pocket.

"Damn," you blurted out as your brother's woman walked out, sporting a tank top and a pair of workout shorts. Both were a bit more loose than you would have liked, but it was certainly nice to see her in something more revealing than her dress. The black tank top showed off a large bit of her cleavage, which she normally hid as she tended to dress more conservatively, and the shorts stopped even higher than her dress did, showing off more of her long pale legs.

"Oh, uhh...thanks?" Felicia said back as she awkwardly shifted as she stood in front of you. You muttered out a quick apology as you told her you couldn't help it.

"It's fine, no worries," she said, "Let's go down to the basement, that's where Hector has all his gym junk."

You followed her down to the basement, eyes glued to her ass as she led the way. As she flicked on the lights downstairs you were impressed with the large array of equipment that your brother had, and a little intimidated as you looked at the massive numbers on some of his weights.

"You better not make fun of me here, I really am a weakling," she said with a laugh. She walked over to the rack of weights against the wall, running her fingers along some of them before trying to grab one of the lightest ones, a rubber weight that said 15 pounds on the side. She wrapped her hands around it and looked like she tried to lift it for a split second before giving up, not wanting to embarrass herself right away.

"I think you'll be stronger than you expect, you're definitely strong enough to lift that one," you said. There was an incredibly feint beep from your pocket, and you watched as Felicia hesitated for a second before lifting the weight. A tiny grunt slipped through her lips as she hefted up the weight in her right hand, and you watched her arm tense up as you saw feint muscles popping out more than before.

"Huh, guess so!" she said, a proud smile on her face as she lifted it over her head. She lowered it down slowly and then passed it over to her left hand, clearly surprised at being able to suddenly handle the weight.

"In fact..." you said, eager to make more changes now that you knew the voice control would work.

(If you like what I've written here and would like to see more, please consider donating at http://ko-fi.com/masterfulmastus).