Frederick William, Duke of Courland
Frederick William was Duke of Courland and Semigallia from 1698 to 1711. Frederick Wilhelm was the son of Frederick Casimir Kettler and Elisabeth Sophie of Brandenburg. During his reign the duchy was occupied by Swedish and later by Russian troops.
Friedrich Wilhelm Kettler was born in 1692 in Jelgava in the family of Friedrich Casimir and his second wife Elizabeth Sophia. At the age of seven, after his fathers death, in theJanuary 1698 he was appointed as the Duke of Courland and Semigallia, however, until the age of majority state was governed by his mother and uncle Ferdinand Kettler, who resided in Danzig.
Source: Wikipedia