Question: The grandfather of  Duke Peter Alexandrovich was the Duke of what European dynasty of North German Origin
Sentence (from "House of 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 names in the line of succession to the British throne, are all patrilineal members of the Glücksburg branch of this house.
Relevant evidence: No