поставьте к приложению вопросы к подлежащему и к специальный вопрос срочно
one day his cousin from came to visit him.

К подлежащему:
Who came to visit him one day?

Специальный вопрос:
When did his cousin from (пропущено откуда) come to visit him?

Общий:
Did his cousin from (London/Kolpino/…) come to visit him one day?