I just found George Larkins age 40 and Nancy Smith age 37 in the 1880 Caldwell, Sumner, Kansas Federal Census. They have three children: J. Lewis, George W., and Minnie A.. There is also a Martin Larkins age 48 in their home.
I also found a George I. Larkin age 75 in the Kansas State Census Collection, 1855-1925 in Sedgwick Co, Wichita, Kansas. In 1915 he is living with Roger S. Davis and Rebecca J. Davis who would be Nancy's sister.