|Wilhelm Kettler (1574-1640)|
In 1609 Wilhelm married Sophia of Prussia (1582-1610), one of the 5 surviving daughters of Albrecht Friedrich (1553-1618), the last, mad Duke of Prussia, and his wife Marie Eleonore of Cleves (1550-1608), a sister of the last, mad Duke of Cleves. As a dowry Wilhelm and Sophia received the territory of Grobina (now in Latvia). Their only child, a son Jacob, was born on October 28, 1610, while Sophia died soon afterwards, around November 24.
Due to conflicts with the local nobility, Wilhelm lost control of the Duchy of Courland in 1617. He emigrated, leaving his brother Friedrich als sole ruler. Wilhelm died on April 7, 1640 in Kukułowo in Poland. Two years later his son, Jacob von Kettler (1610-1682), succeeded his uncle Friedrich as Duke of Courland.