There are lots of examples of country musicians doing blues music (which later evolved into blugrass). Check out Jimmie Rodgers songs, guitar playing and accompaniment, also Riley Puckett did some similar material. The East Texas Seranaders played many ragtime fiddle tunes and were jazz influenced, to be sure Sam & Kirk Mcgee and the Delmore Brothers, Clarence Ashley, did bluesy songs which are now played as bluegrass songs.