Barnim was the sixth child of Duke Philip I of Pomerania-Wolgast and his wife Maria of Saxony, Duchess of Pomerania.

Philip died in 1560 and was survived by five of his sons; in addition to Barnim, they were his older brothers John Frederick (1542–1600), Bogislaw XIII (1544–1606) and Ernest Louis (1545–1592) and Barnim's younger brother Casimir VI (1557–1605).

It consisted of the Lord Chamberlain Ulrich von Schwerin as a regent and a regency council of eleven people.

John Frederick had lived beyond his means, leaving substantial debts and districts pledged to his creditors.

However, Casimir in decided favour of his older brother Bogislaw XIII, who, in turn, appointed his son Philip II as Regent.

[1] The modern interpretation of Barnim as "the tenth" results if one counts only the members of the House of Griffins, who reached adulthood.