The royal descendants of John William Friso, Prince of Orange currently occupy all the hereditary European royal thrones, with Friso and his wife, Landgravine Marie Louise of Hesse-Kassel, being the most recent common ancestors of all the European monarchs. Due to the intermarriage of the European royal houses, many monarchs are descended from Friso in more than one way. Through history, Friso has also been the ancestor of many monarchs whose thrones no longer exist.