The story of this Buddhist priest wandering from one province to the next and his marriage into the Matsudaira clan is probably just a fictional story that was created during Ieyasu's generation in order to establish a genealogically link with the Nitta clan and the Matsudaira clan, which were originally unrelated.
しかし、諸国を流浪する遊行僧だの、入り婿に入っただのという設定は、所詮本来無関係な新田氏と松平氏を系譜上つなげるために、おそらく家康の代に唱えられた創作に過ぎない。