Find a Grave, database and images (https://www.findagrave.com : accessed 02 April 2020), memorial page for Olga Constantinovna Romanov Oldenburg (3 Sep 1851–18 Jun 1926), Find a Grave Memorial no. 8142920, citing Tatoi Royal Cemetery, Athens, Regional unit of Athens, Attica, Greece ; Maintained by Find A Grave ..
It may be possible to confirm family relationships with Olga 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 Olga: