A few Y-chromosome STR markers of Tsar Nicholas II have been released (see Ysearch ID). The Tsar appears to belong to haplogroup R1b, a haplogroup only found in about 5% of the Russian population, but very common in Western Europe.

The last 7 Emperors of Russia, from Peter III (1728-1762), descended from the Dukes of Holstein-Gottorp, themselves descendants of Christian I (1426-1481), King of Denmark, Sweden and Norway, whose ancestors were the German Counts of Oldenburg.

The geographic origin of the lineage in North-West Germany hints that the R1b subclade could be R1b1b2a1a, determined by the mutation U106+ (also known as S21+). The Tsar's DNA hasn't been tested for this particular mutation, so we cannot be sure of it yet.

The Y-chromosome being inherited from father to son, it can be speculated that the members of the House of Oldenburg all belong(ed) to haplogroup R1b, if no infidelity took place.

This is of the highest interest to genetic genealogists, because it includes the present King of Norway, as well as the Queen of Denmark's late father Frederick IX.

The royal families of Denmark, Sweden (+ Finland) and Norway all belonged to this same lineage since the 15th century. The Swedish branch died off in 1818 with Charles XIII - who was succeeded by Napoleon's former marshal, Jean-Baptiste Bernadotte.

In addition to the Russian and Scandinavian monarchs, other royals sharing the same Y-DNA include among others :

- the Kings of Greece since George I (1863-1913)
- the (Grand) Dukes of Oldenburg
- the Dukes of Schleswig
- the Dukes of Holstein
- the Dukes of Holstein-Sonderburg-Beck
- the Dukes of Holstein-Sonderburg-Plön
- the Dukes of Holstein-Gottorp
- the Dukes of Schleswig-Holstein-Sonderburg-Glücksburg

A famous member of the House of Schleswig-Holstein-Sonderburg-Glücksburg is Prince Philip, Duke of Edinburgh. This means that Charles, Prince of Wales, and his sons William and Harry (again, possible infidelity notwithstanding), belong to that same Y-DNA lineage.