Born in 1135, Rotrou was the son of Count
Rotrou III of Perche, and Hawise, daughter of Walter of Salisbury, and Sibilla de Chaworth. Upon the death of his father in 1144, Rotrou continued the fight against his archenemy, Count
William III of Ponthieu, lord of Alençon. Aside from this long-running blood feud, his uncle Patrick had married William' daughter Adela. His mother Hawise and her second husband, Robert I of Dreux, served as regents at Perche until he reached the age of maturity. Rotrou aided King
Louis VII of France against King
Henry II of England in an ineffective war that saw their troops routed, lands ravaged and property stolen. He was forced to yield the communes of
Moulins and
Bonsmoulins to the crown England. Nevertheless, a matrimonial alliance with the
House of Blois consolidated the declining power of the counts of Perche. In 1189, Rotrou joined Kings
Philip II of France and
Richard I of England in the
Third Crusade. He died sometime after the
Siege of Acre in 1191. ==Marriage and issue==