On the men’s side, the confusion is in all the men named or whom renamed themselves Louis or Napoleon.
The first Napoleon I had a son with his 2nd wife (Marie Louise) who was his official heir. He was named François Charles Joseph & Napoleon II, but he died as a child.
Napoleon I’s brother’s name was Louis-Napoleon. He called himself Napoleon, as his name, but he did not have title and did not really want it as he was very happily already a political ruler. Louis-Napoleon married Napoleon I’s stepdaughter, Hortense at the request of Napoleon I.
Hortense & Louis Bonaparte (the brother) had a son whom they named Charles-Louis. He called himself Napoleon III & married Eugenie (the ones we are discussing this week). He was the rightful heir, even though he was in political power while Napoleon II was still living, because Napoleon II wanted nothing to do with the throne.
Charles-Louis (Nap III) & Eugenie named their son Louis-Napoleon and called him Napoleon IV. THAT Louis-Napoleon died as a young man.
Got it? Just wait until we get into the Victorias and Eugenies…
(photo: Eugenie with Napoleon III & their son Napoleon IV; below – same photo session Napoleon III with just his son Napoleon IV)