Shepherd and William Mize were probably brothers and sons of Randolph and Martha. Shepherd married Elizabeth Mays first in 1833, Surry Co NC. William married Mary Ann ______ and moved to Carter Co TN. Shepherd moved to southern Illinois, where two other likely brothers were, John and Jeremiah. Shepherd is on the 1830 Wythe tax list with Martha (Patsy).
The later Mizes in Wythe and Smyth were from the Granville NC branch of Mizes if I recall correctly. They are distant cousins of Randolph's.