Who is it?(BTS Fanfic)

Jung Hoseok's younger sister, Jung Hakyo has just graduated from high school.
She gets into a college that ends up being close to her brother's band's dorm.
Without wanting to, she's forced by parents to move in with them.
Hakyo... The opposite of her brother... Not cheerful. Not happy all the time. She wasn't even that girly.
Once she moves in with the seven, she realizes that there is just one person who can make her happy all the time.
One person to make her cheerful.
Maybe even act girly sometimes.
That person is in BTS
That person is him...
Who's him?
Who is it?
This is a story where I will use "he" and "him" and such without the actual person's name when there is a romantic part so have fun guessing who it is until I say.