Guillaume de Courtenay
From NSWiki
Prince Guillaume de Courtenay (born 1983) is the son of Prince Gaston de Courtenay.
In 2009 he married Monika von Prach. They have four children: Victor (born 2011), twins Raoul and Jérôme (born 2013) and Joséphine (born 2016).
Guillaume works with his father.