His father, Reginar III, was exiled in 958 as a rebel by
Otto I, Holy Roman Emperor. Hainaut was held after then by
Godfrey I, Duke of Lower Lorraine, but Reginar IV claimed that Mons in Hainaut had been his father's. He attacked Mons in 973, after the death of Duke Godfrey, but did not manage to hold it, because
Godfrey I, Count of Verdun then held it until he died. He managed to replace Godfrey as Count of Mons in 998. ==Family==