Zilphea was born in 1882. She passed away in 1977.
"United States Census, 1910," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M2MQ-3ZB : accessed 14 December 2018), Zilphia Stephens in household of Thomas P Stephens, Justice Precinct 6, Dallas, Texas, United States; citing enumeration district (ED) ED 99, sheet 10B, family 197, NARA microfilm publication T624 (Washington D.C.: National Archives and Records Administration, 1982), roll 1545; FHL microfilm 1,375,558.
"United States Census, 1940," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:KQVG-Q7G : 15 March 2018), Zelphia Stephens in household of Tom P Stephens, Mammoth Spring Township, Fulton, Arkansas, United States; citing enumeration district (ED) 25-9, sheet 10B, line 44, family 200, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 136.
It may be possible to confirm family relationships with Zilphia by comparing test results with other carriers of her mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Zilphia: