At what stage of his life did bill monroe first show his musical ability

Bill Monroe is a great musician. He also knows how to play a mandolin. Through writing  a song, he made a new genre of music called bluegrass. As most of the people would tag him as the father of blueggrass. His family, mother and brother loves to play music, so no wonder , even though Bill was still a child, he loved music and inclined to it.