Answer:
Bob Wills (a.k.a. Jim Rob, or James Robert) of Bob Wills and the Texas Playboys was 1 of 10 children: 3 brothers and 6 sisters. The siblings were Johnnie Lee, Luther J. (a.k.a. Luke), Billy Jack, Ruby, Eloise, Olga, Helen, Lorene, and Jesse Wayne. As of March, 2010, all of the siblings are deceased.
(per website http://www.texasplayboys.net/Biographies/uncle_john_wills.htm, http://www.cowboydirectory.com/W/w-ills.html).