Question!!!!!!!!!!!!

Hi!! Have a quick question. There's this yaoi manga I read a while back, and I think it's a side story of another story or something like that. So the main character is in love with his brother, but is afraid to let him know and he has a sexual relationship with his home tutor who knows of his crush. if I'm not wrong, his brother plays the piano very well. I'm really sorry but this is all I can remember. Thank you so much if anyone can remember the title of the story!!!!! (=・ω・=)