The assassin was Ptolemy's dynastically frustrated son by his first wife; competitive sons from multiple marriages were the curse of the Successors.
Frederick II was the last of a line, not just dynastically but in a broader and more important sense.
While filling seats vacated by Cabinet nominees and indicted politicians is a favorite of the dynastically inclined, regular elections are not immune to the phenomenon.
So dynastically speaking, he seems to meet princely criteria.
If the majors had become expert at corporate intermarriages through their joint ventures, Mattei would go them one better: Thinking dynastically in his quest for Italian access to Iranian oil, he floated the idea of marrying off an Italian princess to the Shah, who was in urgent need of a male heir.