There were many States in Historical Italy,each with a separate nobility.
They differed in structure, wealth and power.
After the unification of Italy previous Nobility laws and customs were maintained.
Historically, since the introduction of the Feudal System,Titles were granted by Emperors ,Kings(German,Austrian,French,Spanish) and Popes,in addition Powerful Lords (Milan Dukes, Tuscany ,Venice,Parma…) also conceded Titles To local Aristocracy.
The hereditary Titles of Principe,Duca,Marchese,Conte,Barone were granted by Patent Letter by Emperors,Popes and Kings out of the Feudal System of the Holy Roman Empire.
The Status of Patrizio is related to the City of origin.
The Title of Don means Noble Rank and The Consulta Araldica(Italian authority after the unification ,which supervised the Titles recognition and concession) in 1929 granted this historical custom (Don and Donna) only to those Feudal Families(mainly Naples and Sicily) of Princes ,Dukes , the Roman Nobility and some Lombard Families.
When the Italian Republic was established in 1946,all Titles were abolished, but the Noble Families recognized before 1928, were authorized to incorporate the title on the surname.
Naples (Dukedom then Realm)
All Conquerors of Southern Italy adopted the Feudal System, Land possession was divided in Fiefs since the Lombard invasion in 590-839 AD (the first Dukedom was established in Benevento in 758 AD).
With the Normans invasion (Tancredi and Roger d’Hauteville 1060-1194) a further implementation was undertaken, but mainly from the Lombard feudal structure than the Frankish.
The Hohenstaufen with Conrad and Frederick (1194-1266) introduced the Female Succession.
The conquest of the Realm by Charles I of Anjou (1266) ,in order to avoid collaterals succession established the concept of legitimate descendants.
Under the Angevins (1262-1441) and Aragonese(1442-1495) ruling not changements were made.
With the Emperor Charles V (Spanish Ruling 1503) the system was modified as the last descendant died ,remote and collateral lines must succeed male and/or female.
During the Reign of Philip II of Spain (1595) and Charles VI of Austria( 1720) was introduced the Male succession in spite of Female with equal right.
The titles of Princes and Dukes were granted outside the Royal Family already under the Angevins and Aragonese ruling (Queen Jeanne I 1343 and Alfonso the Magnanimous 1442): Prince of Taranto (1373) to Giacomo del Balzo;
Duke of Andria(1343) to Francesco del Balzo;
Prince of Salerno (1442) to Antonello Sanseverino….
Under the Spanish Viceroyalty and ruling (1504-1707) titles were distributed lavishly.
With the arrival of The Bourbons (1740-1799 and the restoration 1805-1861) the practice of a husband to adopt the title of the woman was officially legitimate. The titles of Prince in the Royal Family were allowed only to primogeniture of Males.
During the Napoleon Ruling (1799-1815) the Feudalism was officially abolished by Joseph Bonaparte (1806), but all titles granted were confirmed
by Ferdinand IV of Bourbon ,King of the Two Sicilies.