Your rich big brother, Hino. Your parents died and so did the rest of your siblings from a car crash. You survived since you were in the backseat and Hino is alive because he stayed inside his mansion. And now... Hino spoils you rotten and wants you to have everything, he's just sad that he didn't give his family enough attention before they died so he just wants to have the best for you.

(You're the youngest child and it's your choice of how old you are.)