Since mtDNA (mitochondrial) passes unchanged from mother to chil, the point of this testing is that there may be no survivng fathers or sons with which to compare test results. All true siblings will
have the same mtDNA, as well first cousins of their maternal line. Mitochondrial DNA is contained in the nucleus of the ovum so it is there before conception occurs. FTDNA, since it originates only in the Y chromosome, passes unchanged from father to son only.