He's his sister's assistant/test subject.

With world in constant move, technology advancing by leaps and bounds, the job market was looking dire. Few that were not geniuses bothered to go to university because they best efforts would account for very little compared to them. Low skilled jobs were quickly being phased out due to the arrival of AI or robots and while the government was talking about some form of universal income, the funding wasn't there yet to put it in place for everyone.

K-T's parents had insisted with Emily that she helped her poor brother without prospects since her future was assured. She had accepted to take him as an assistant if he agreed to also help her test her various inventions. I'd didn't pay a full salary, but he could make a bit of cash without leeching from his parents forever. And since he was now an adult his parents had given him the choice either be his sister's assistant or find a real job, otherwise they would no longer let him stay living at home rent free.

While he didn't really like being at his sister's beck and call, he had checked about it. There were no job openings where he wouldn't compete with thousands of more qualified candidates and no place he could afford to live on his own at. And with his room being a basement of the same footprint as the entire house he didn't want to ask what kind of rent his parents would ask.

K-T was masturbating on his bed, hoping that no one would come down, when the red light above his bed lit up, a buzzing noise coming out of the speakers. It was the signal that his sister needed him.

Knowing that trying to finish was only asking for his sister getting downstairs looking for him, catching him at the most embarrassing moment, he wiped his hands, put his shorts back up and climbed upstairs to Emily's big lab/bedroom combo. (half of it being his old room.)