Ferdinand I was King of the Two Sicilies from 1816 until his death. Before that he had been, since 1759, King of Naples as Ferdinand IV and King of Sicily as Ferdinand III. He was deposed twice from the throne of Naples: once by the revolutionary Parthenopean Republic for six months in 1799, and again by a French invasion in 1806, before being restored in 1815 at the end of the Napoleonic Wars.

Philip of Naples and Sicily, "Duke of Calabria", Infante of Spain was the eldest son and heir-apparent of Charles III of Spain, but was excluded from the succession to the thrones of Spain and Naples due to his intellectual disability. His younger brothers, Charles IV of Spain and Ferdinand I of the Two Sicilies replaced him in the succession. When his father became King of Spain in 1759, Philip remained in Naples where he lived until his death from smallpox at the age of 30.