Here's an interesting tale from Wikipedia's biography of the great Romantic painter Delacroix:
There is reason to believe that his father, Charles-François Delacroix, was infertile at the time of Eugène's conception and that his real father was Talleyrand, who was a friend of the family and successor of Charles Delacroix as Minister of Foreign Affairs, and whom the adult Eugène resembled in appearance and character. Throughout his career as a painter, he was protected by Talleyrand, who served successively the Restoration and king Louis-Philippe, and ultimately as ambassador of France in Great Britain, and later by Talleyrand's grandson, Charles Auguste Louis Joseph, duc de Morny, half-brother of Napoleon III and speaker of the French House of Commons.
Talleyrand is a major historical figure, who, among much else, negotiated for France at the Congress of Vienna in 1814-15 a very mild retribution from the victorious Great Powers after two decades of war. The moderate and durable settlement that Talleyrand talked the crowned heads of Europe into agreeing to after France's Revolutionary and Napoleonic adventures is often contrasted favorably with the harsher and shorter-lasting peace dished out at the Versailles Conference after WWI.
Can you think of other examples where one famous individual turns out to have been the quasi-secret child of another? It's a pretty interesting phenomenon, one that is hard not to pay attention to, but likely examples don't come readily to mind.
For example, if you told me that San Francisco 49ers quarterback Colin Kaepernick, a 6'-4" biracial adoptee of tremendous athletic ability, is really the son of, say, Michael Jordan's 6'-8" sidekick Scottie Pippen, I might almost believe you. (Note: I just made that up.) But, there are surprisingly few confirmed examples of today's sports stars being the secret sons of yesterday's sports stars.
One reason for the Scandal Shortage is that there just aren't that many famous people. Talleyrand and Delacroix, for example, are of that tiny number of figures of such historical importance that we only use their surnames.