Thomas Rhett was so astonished to find his younger brother Tyler Lankford blasting his music during a recent family beach outing that he had to document it on social media. “Rare sighting of my little brother listening to my music,” country singer writes in text on the video with the caption #onlylistenstozachbryan. He follows Lankford down the walkway to the shore filming him as he carries a boombox that is blasting Rhett’s song “Gone Country.” Feeling his presence behind him, Lankford turns around to ask what he’s doing. Rhett fires back the same question — further driving home his point. Fa…