Father of two Tsars - Alexander I and Nicholas I, and of Maria GDss of Saxe-Weimar, Catherine Queen of Wurttemberg and Anna Queen of the Netherlands
Alexander III, father of Nicholas II and if you count Michael as the last Tsar.
King Friedrich Wilhelm III of Prussia was the father of two Prussian Kings. His eldest son became King Friedrich Wilhelm IV of Prussia. He died without any children so he was succeeded as King of Prussia by his brother as King Wilhelm I of Prussia who also became German Emperor in 1871.
King Philippe IV of France had three sons who also became King of France.
The eldest was Louis X, King of France. He died while his wife was pregnant and his son, Jean I was born King but sadly only lived a few days.
The infant King was succeeded by his uncle, brother of Louis X, who became Philippe V, King of France. He left daughters so he was succeeded by his youngest brother as Charles IV, King of France
Charles IV only had daughters and was succeeded by a distant cousin as Philippe VI, King of France.
King Henri II of France had three sons succeed him. His eldest son became King François II of France (King Consort of Scotland from his marriage to Queen Mary I of Scotland). François was succeeded by his brother as King Charles IX of France. Charles only had a daughter who was not allowed to succeed in France because of the Salic Law. He was succeeded by his brother who became King Henri III of France who had been briefly King of Poland.
In the House of Stuart as well as the Coburgs, several English monarchs fathered more than 1 monarch. Charles the 1st fathered Charles II along with James II. James II was father to both Queen Mary II and Queen Anne. this arrangement was probably by Parliamentary directive? George III was followed on the throne by sons George IV and William IV. George V was followed by sons Edward VIII and George VI. From a technical point of view both Victoria and her son Edward VII had similar situations though one child was consort in a foreign nation. Edward VII had son George V as king of England while his daughter Maud was consort to Haakon in Norway. Victoria's eldest son was Edward VII of England while her eldest daughter briefly served as Queen of Prussia and Empress of Germany. Were there others, please? there must have been similar situations within earlier English royal houses?