Sources

1) Source: Chronica Magistri Rogeri de Houdene "After Easter, Philip, king of France, took to wife the daughter of the earl of Hainault, and niece of Philip, earl of Flanders, being the daughter of his sister" (Data from direct source)
2) Source: Genealogia comitum Flandrensium ex libro Florido et Chronico Aldenburgensi, etc "Cui succesit balduinus comes hanonie, nepos ejus, postea constantinopolitanus imperator et duxit filiam comitis campanie, nomine Mariam, ex qua genuit duas filias Johannam et Margaretam."
3) Source: Genealogia comitum Bulonensium A short genealogy connecting the early Merovingians to the later counts of Boulogne, written circa the 11th century. The earliest generations are almost certainly fictional. Considered a reliable secondary source for generations from Arnulf of Metz onwards. Considered a "primary" source for events from the year 1000 onwards.. External Link
https://www.dmgh.de/mgh_ss_9/index.htm#page/300/
4) Source: Chronica Magistri Rogeri de Houdene "In the same year [1187], Isabella, the queen of France, and daughter of the earl of Hainault, was delivered of her first-born son on the third day before the nones of September, being the fifth day of the week, who was named Louis" (Data from direct source)