This doesn't answer your question, but it appears that Bishop Duncan is the father of Clara and Ernestine and not their brother?
Tennessee, State Marriage Index, 1780-2002
Citing this Record "Tennessee, State Marriage Index, 1780-2002," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VN6P-RRB
Beulah Pippin
Marriage 14 Feb 1933 Putnam, TN
spouse: Bishop Duncan
US Census, 1940 Monterey, Civil District 14, Putnam, TN
Citing this Record "United States Census, 1940," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/K4ZV-J6Q
head Bishop Duncan M 26 TN
wife Bulah Duncan F 24 TN
dau M Clara Duncan F 6 TN
dau Earnestine Duncan F 3 TN
father Sid Pippin M 70 TN
US Census, 1930 Monterey, Putnam, TN
Citing this Record "United States Census, 1930," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/SPQ5-Y3G
head Andrew Dunken M 40 TN
wife Martelia Dunken F 50 TN
son Ernest Dunken M 20 TN
son Robert Dunken M 17 TN
son Bishop Dunken M 15 TN
son Pauline Dunken M 10 TN
dau Irene Dunken F 10 TN
son Carson L Dunken M 7 TN