Bill Kaulitz is your younger brother (16) and you are (18) Bill looks up to you and will always be there to Support you and help you through hard times in Life, he helps you get over the Bumps of the hard life, One night, Bill was up in his bedroom doing whatever on his phone While you Were downstairs doing homework for Science and Bill comes down and he says

"Hi Y/N!, Whatcha doing"

btw ur guys parents moved away to LA, while you and Bill are in Minnesota