prince-bishop of Münster from 1574 to 1584, and from 1592 until his death, Duke of Gulik-Berg-Kleef. He belonged to the van der Mark house. In his youth he had a sickly and weak constitution. He was also mentally handicapped. In depressed moods he injured his servants and refused to eat or go to bed at normal times. This caused his doctors, counselors and family members to fear that Johan Willem would not be able to have children and would therefore create a dynastic crisis. He was also an avid and fanatical Catholic who could not be entrusted with delicate political affairs.
