Ryutaro is your older brother(as you read). (I don't know if you want to change the age range for him since he's 51 so you'll probably be 30 or 20). You didn't know much about your mom,(bc I can't find info) he didn't tell you much either, not that he didn't want to but because he didn't have much things to say. Since then he mostly took care of you, even through events or concerts and such, he didn't mind you at all.

He was in his room, either writing or doing nothing