Rock Hard by M.J. Roberts

Drummer Ryder Chord has been living half a life since he was sixteen when a brutal tragedy strikes his family and he and his best friend hit the road. Ryder, desperate to forget, throws himself into touring life and writing music. When Lexi joins the band, Ryder’s life becomes almost tolerable. Until one day when the rest of the band isn’t there and Ryder and Lexi have to share a hotel room: with only one bed.
Rule number one of band-dom: You never sleep with anyone in the band.
Rule number one of bro code: You never sleep with anyone’s sister. You definitely never sleep with your best friend’s little sister.
Rule number it’s so obvious it’s a count even a drummer can keep: You Never. Ever. Sleep with your best friend’s little sister when she’s in the band…and he is too.