She was the daughter of (Florent I) Floris I, Count of Holland, by his wife Gertrude of Saxony, the daughter of Bernard II, Duke of Saxony. After her father died in 1061, her mother remarried to Robert I, Count of Flanders, called Le Frisian. In 1072 her stepfather concluded a peace treaty with King Philip. As part of the terms of the treaty Bertha was married to Philip.

Nine years passed before Bertha produced the desired son and heir, Louis. Reportedly, her fertility was only restored thanks to the prayers of a hermit, Arnoul, who also named the child. Together, Philip and Bertha had five children:

1. Constance, married Hugh I of Champagne before 1097 and then, after her divorce, to Bohemund I of Antioch in 1106
2. Louis (December 1, 1081–August 1, 1137)
3. Henry (b. 1083) (died young)
4. Charles (b. 1085) abbot of Charlieu Abbey
5. Eudes (1087-1096)

In 1092, Philip repudiated Bertha, alleging that she was too fat. He confined her to the fortress of Montreuil-sur-Mer, and took up with Bertrade de Montfort, the countess of Anjou.

Sources

• Ancestral Roots of Certain American Colonists Who Came to America Before 1700 by Frederick Lewis Weis, Lines: 101-23, 103-23.
• Duby, Georges. The Knight, the Lady, and the Priest: the making of modern marriage in medieval France, 1983.
• Encyclopaedia Britannica: A New Survey of Universal Knowledge, 1942, s.v. "Philip I".