If I may both engage in ASBs and Napoleonic favoritism:
Napoleon Bonaparte: Marries Desiree Clary (1795) (who gives him multiple children). To give himself legitimacy, he divorces her and marries María Isabella of Spain (April 1801). (Desiree Clary later marries Mathurin-Léonard Duphot on the 31st of December, 1797)
Lucien Napoleon marries Maria Luisa of Spain (IOTL, Napoleon insisted upon the match, and it became a big point of contention between the brothers)
Prince Napoléon Bonaparte (Jérôme) and Princess Mary Adelaide of Cambridge
Napoléon François Joseph Charles Bonaparte + Catherine Pavlovna of Russia (1808) - Their son (we know him as Napoleon II IOTL) marries Princess Sophie of Bavaria (Yes, the father is named after the son ITTL, truly something worthy of Inception)
Second son of Napoleon and Anna Pavlona of Russia
Third son of Napoleon marries Marie Louise of Austria (Yes, ITTL, one of Napoleon's sons marries what IOTL was his mother. That's how big the age gap was, which is pretty gross IMO)
Fourth son of Napoleon and Princess Caroline Augusta of Bavaria (ITTL, Napoleon has a son for every potential/speculated marriage match he was offered)
Fernando de Asturias (Fernand VII) + Charlotte Bonaparte (First daughter of Lucien Bonaparte)
Ferdinand III of Tuscany + Charlotte Bonaparte (First daughter of Lucien Bonaparte) (ITTL, they're identical tins/cloned/whatever)
Napoleon III + Princess Adelheid of Hohenlohe-Langenburg (Niece of Queen Victoria + Mother-in-law of Wilhelm II)
Napoleon III (brother/clone) + Princess Carola of Vasa
Napoleon II (brother/clone) + Eugénie de Montijo
For non-Napoleonic marriages
Constantine IV and Rotrude (Daughter of Charlemagne)
Charlemagne and Irene
Charles II of Spain and Infanta Isabel Luisa of Portugal
William Seymour and Lady Arbella Stuart
Queen Elizabeth I and Robert Dudley (1559) (He avoids the rumors ITTL, and Elizabeth is happy, and as such perhaps Lady Katherine Grey would be allowed to succeed to the throne as was intended by Henry VIII in his will [assuming Elizabeth still doesn't have kids])
Ivan Ivanovich (son of Ivan the Terrible) and Virginia Eriksdotter (daughter of Eric XIV of Sweden)
Frederick the Great and Maria Theresa of Austria
Prince Frederick of Prussia (1794–1863) and Princess Charlotte of Wales
Miguel I of Portugal + Maria II of Portugal (Marriage by proxy since she was 7 years old when this was proposed in 1826) (Combined with the following match, it could cement an Iberic Union for at least a few decades)
Pedro V of Portugal/Prince Leopold/Infante Enrique + Isabella II of Spain (Either one is cool, though Pedro V is the coolest option due to the potential for another Iberic Union)
Archduke Maximilian and Princess Maria Amélia of Brazil (Maybe they have kids, and it would give him more legitimacy as Emperor of Mexico since his bride would be Latin-American)
Archduke Ludwig Viktor of Austria and Isabel, Princess Imperial of Brazil (Perhaps it could help Brazil keep its monarchy and avoid the subsequent instability)
Prince Albert Victor, Duke of Clarence and Avondale and Princess Margaret of Prussia (Always nice to see friendlier Anglo-German relations)
Archduke Franz Ferdinand of Austria and Princess Hélène of Orléans (Always interesting to see an Franco-Austrian alliance)