Russian Empire
Though the Empire was only officially proclaimed by Tsar Peter I following the Treaty of Nystad (1721), some historians would argue that it was truly born either when Ivan III of Russia conquered Veliky Novgorod in 1478, or when Ivan the Terrible conquered the Khanate of Kazan in 1552. According to another point of view, the term "Tsardom", which was used after the coronation of Ivan IV in 1547, was already a contemporary Russian word for empire.
Rurik dynasty
In that year, Mikhail I ascended the throne, founding the Romanov dynasty that would rule until 1762 and as Holstein-Gottorp-Romanov until the revolutions of 1917. Tsar Mikhail's first wife Maria Dolgorukova was of Rurikid stock but their marriage produced no children. Emperor Peter III in 1762 brought fresh Rurikid blood to the Romanovs: he and his wife Catherine the Great both descended from the Rurik dynasty. (Catherine the Great descended from a daughter of Yaroslav I (978–1054) through her maternal grandfather, Christian August of Holstein-Gottorp.)