Napoleon I was Emperor of the French from 1804 to 1814 and again in 1815.
Marie Louise of Austria was his second Empress. Their son, Napoleon François was born March 20, 1811.
Suppose Napoleon is Emperor of the French until 1816.
He and Marie Louise have a daughter, Her Imperial Highness, Princess Imperial of the French, Marie Zéphyrine Thérèse, born in 1814.
Napoleon I abdicates in 1816. He dies in 1821.
Suppose Napoleon François dies in 1822.
What happens to his sister, Marie Zéphyrine? Who shall be her husband?
So are you saying in 1816, Napoleon abdicates for his son Napoleon II or abdicates after losing a longer napoleonic war?
If its the first then in 1822, Her Imperial Highness, Princess Marie would be 8 years of age so would rule under a regent of most likely her mother and one of her uncles.
She would likely marry between the aged of 18 and 30 (1832 and 1844)
- Her cousin Louis-Napoléon Bonaparte (OTL Napoleon III) is 6 years old and would keep the Bonapartes on the French Throne.
If you want to link France with a German State:
- His Royal Highness Prince Maximilian of Bavaria (future King Maximilian II)
- Or his brother, hi
s Royal Highness Prince Luitpold of Bavaria (OLT Prince Regent to King Lugwig II and King Otto)
- Or his other brother, hi
s Royal Highness Prince Otto (OTL King Otto of Greece)
- Prince Charles of Hesse and by Rhine
- Prince Alexander of the Netherlands
To marry into her mother's Austrian family would mean going for someone much older or much younger, such as:
- Archduke Stephen, Palatine of Hungary
- Archduke Albrecht, Duke of Teschen
- Archduke Franz Karl of Austria
- Having her marry a French Bourbon, could be interesting and Prince Louis of Orléans, Duke of Nemours could be a fine candidate


- Or a Spanish Bourbon, Infante Carlos, Count of Montemolin, who has claims to the throne of Spain

These monarchs are recent widowed or single:
- Victor Emmanuel I of Sardinia
- Ferdinand II of the Two Sicilies
- Leopold II, Grand Duke of Tuscany
Or even more enteresting have her marry a French General or Politican who was favourites with her father?