The House of Oldenburg is a European dynasty of North German origin. It is one of Europe's most influential royal houses, with branches that rule or have ruled in Denmark, Iceland, Greece, Norway, Russia, Sweden, Schleswig, Holstein, and Oldenburg.
The current Queen of Denmark and King of Norway, the former King of Greece, the consorts of Greece and the United Kingdom, as well as the first twelve persons in the line of succession to the British throne, are all patrilineal members of the Glücksburg branch of this house.
The progenitor of the Oldenburg line was Elimar I, Count of Oldenburg b. 1040. The Russian House of Romanov, with Tsar Nicholas II b. 1868 as the last Tsar and the Danish House of Glücksburg are both from the Oldenburg line. The future King of Great Britain, Prince Charles of Wales is also from the Oldenburg line.
As such - both these royal lines "should" all share common Y-DNA STR markers and also the same Haplogroup, as their common ancestor on paper is King Frederick I of Denmark and Norway b. 1471.
Appendix 2 - Was Kaye's Grandfather an Oldenburg? provides detail relating to whether the person identified (i.e. Kaye's paternal Grandfather) was from the Oldenburg line.
New information has been provided in April 2019, which shows Kaye's Grandfather STR values are a Genetic Distance of 9 from a known Romanov (i.e. Oldenburg) man @ 37 markers. This should prove that Kaye's Grandfather is NOT an Oldenburg. However, do the Russian Oldenberg and Danish Oldenberg lines match? Why wasn't Prince Phillip (Duke of Edinburgh) YDNA also used to match Tsar Nicholas II YDNA, rather only his mtDNA was used (refer Figure S1)?
It is still possible that Kaye's Grandfather may be related to some as yet unknown European Royal line, noting his Haplogroup SNP listing is P312 > DF19 > DF88 > FGC11833 > S22352 > Z30474.
Also, Kaye's Grandfather remains a close match to "Headless Roman Skeletons" from Driffield Terrace, York, UK (i.e. 6DRIF-23).
We may not yet have gotten to the bottom of the Romanov YDNA story is my interim conclusion.
