Reginar IV, count in Hainault, was born about 950, the son of Reginar III, count in Hainault, and Adela de Louvain. His father was count in Hainault until 958, but fell into disgrace with Emperor Otto I and was stripped of his county, which was given to Godfrey I, duke of Lower Lorraine. Reginar received the county of Mons in 973 but was replaced with Godefroy, count of Verdun and Ardennes in 974. He replaced Godefroy as count of Mons in 998.
About 998 Reginar married Hedwige de France, daughter of Hugues Capet, king of France, and Aelis de Poitou. Of their four children, Reginar V and Beatrice would have progeny. Their daughter Ermentrude, who died at age two or three, was buried in the Collegiate Church of Saint Gertrude in Nivelles, Belgium. The burial came to light during an excavation. A lead cross, inscribed with her name and that of her parents, was found in the tomb.
Reginar died in 1013.
Aelis was born about 945. Her parentage is not known. It is now established that she was not the daughter of Guillaume I-III, duc d'Aquitaine. About 968 she married Hugues Capet, son of Hugues 'the Great', duke of The Franks, comte de Paris, and Hadevich von Sachsen. In 987, after the death of Louis V, the last Carolingian king of France. Hugues was elected the new king with Aelis as queen. They were proclaimed at Senlis and blessed at Noyon. They were the founders of the Capetian dynasty of France.
Aelis and Hugues had four children, of whom Hedwige, Gisle and Robert II would have progeny.
Aelis died on 15 June 1006.