As he was still a minor when he inherited Werle, his mother put him under the guardianship of Duke Albert II of Mecklenburg.
However, a dispute arose between Albert II and John's mother, and she then chose Lord Nicholas III of Werle-Güstrow as his guardian.
After Nicholas's death, John IV ruled for himself.
On 31 October 1366, he closed a marriage contract with Duke Albert II and his sons, in which he was promised he could marry Euphemia, the four-year-old daughter of Albert's son Henry III.
However, John IV died in 1374, so the marriage never took place.