Holy Roman Emperor Friedrich II had appointed his illegitimate son Enzio king of Sardinia in 1239; the latter would lose the title as soon as 1249, however. In 1284, Genoa defeated Pisa, acquired Corsica, Elba and Sardinia. In 1323, Sardinia was acquired by Aragon, and 1399, Florence bought Corsica from Genoa. (The current ruler, Cosimo de Medici, planned to build up a fleet and becoming a naval power in the Mediterranean.)
After the division of Aragon 1599, Sardinia went to France, which sold it to Florence, though. But quite soon, during 1616-19, the "Island uprising" in Corsica and Sardinia happened, after trying to reform the administration too fast (after French example). Florence proved unable to overwhelm them again, just could get the promise from France that they wouldn't try to conquer them. Instead, 1639 Sicily conquered Corsica and Sardinia with their fleet. France and Spain were preoccupied and couldn't interfere.
A son of Sardinia would become very famous later, when he became general first and later first New Roman Emperor Alessandro I.