Similar to デンマーク・ノルウェー連合王国

Kingdom of Italy (Napoleonic)

Dual monarchy of England and France

Commonwealth realm

Union of the Crowns

Kingdom of the Netherlands

Principality of Catalonia

Union of Kėdainiai

Holy Roman Empire

Union between Sweden and Norway

Sweden-Finland

Denmark–Norway

Kingdom of Hejaz and Nejd

Realm of New Zealand

Seventeen Provinces

Habsburg monarchy

Swedish Empire

Lands of the Crown of Saint Stephen

Grand Duchy of Finland

Brandenburg–Prussia

Duchy of Burgundy

Lands of the Bohemian Crown

United Kingdom of Portugal, Brazil and the Algarves

United Duchies of Jülich-Cleves-Berg

Icelandic Commonwealth

Christianization of Iceland

House of Knýtlinga

Jelling stones

Vikings