The Three X Sisters were actually The Hamilton Sisters and Fordyce (i.e., Jessie Fordyce) who were later renamed to add glamor and mystery to their radio careers. Pearl Hamilton (1900-1978) started out in the late teens and early twenties in old school (non-stripping) burlesque. She teamed up with her sister Violet (1908-1983) and their friend Jessie in 1924. Their radio debut was in 1927. They were also in demand for cartoon voice overs during the 1930s. They gradually broke up the late 1930s, early 1940s. Pearl and Violet continued to pursue separate careers for a while. Little is known of what happened to Jessie.
The clip below is from their peak, around 1935:
To find out more about the history of vaudeville, consult No Applause, Just Throw Money: The Book That Made Vaudeville Famous, available at Amazon, Barnes and Noble, and wherever nutty books are sold.