I was reading through wikipedia a bit, and as I can see he wasn't a prince at all, at least not what I imagine a prince is: son of a king or heir to the throne or ruler of some land. The closest is that he was a second cousin of Duke of Savoy.

Yet (again through wiki article) it seems as though all his contemporaries reffered to him as "Prince"

At best I can figure out, just him being Savoyan's royal family cousin was enough for him to be Prince. Was it common then? Did the title then had any meaning?