He was a son of Count Edzard II of East Frisia and Princess Katarina of Sweden, and a younger brother of Count Enno III of East Frisia. John married in 1601 with Sabina Catherine, the daughter of his brother Enno III. Under the Treaty of Berum, Sabina Catherine had been awarded the County of Rietberg, which her mother Walburgis had brought into the Cirksena family.
He founded the Catholic side line of the Cirksena in the Westphalian County of Rietberg, the so-called house of East Frisia. Together, they reverted the reformation in the county of Rietberg. That he didn"t convert only for political reasons, was made evident when he founded a Franciscan monastery in Rietberg.
Being a catholic, John could make his career in the imperial service.
He became an officer in the imperial army and later in the Spanish army.
