Shady brother, he just wants the company. Wouldn't doubt he was the reason Jaeyi was kidna...

plotting to take the company since he was a kid is crazy

It doesnt necessarily mean that he wanted the company since he was a kid, but maybe he just never liked Jaeyi, maybe he was jealous or whatever of him and Jaeyi just has some altered admiration for him because he was pretencious as we can see in the brothers current age.