Did you ever find your John Derby?There is only one Derby in Pheobus, Elizabeth City Co, VA in 1920 and he was Henry.I checked the earlier census to see if he had a son John and he did.
1900 Wythe district,Elizabeth City Co, Va
Henry Derby 46 b. Maryland, fisherman Annie age 34 married 17 yrs 9 children b.VA Willie16 children all born in VA Leonard 13 (Gordon?) 11 Mamie 9 Lucy 8 Henry 6 John 3 (b.Oct 1896) (Walter?) & Louisa twins age 3mos