In case you that isn't enough and you want to get to know even more about Luxembourg's Hereditary Grand Duke, you should listen to the following three interviews for Eldoradio, DNR and RTL Radio. Small hint, the DNR interview isn't just audio but a video. Also have a look at the picture gallery of Eldoradio's Prënzeparty and the ones from the RTL Radio interview.
In the interviews Guillaume reveals which sibling he is closest to, that it can get pretty intense being four boys in a family, why Alexandra is the princess of the family, what he likes to cook and when he goes to the supermarket, that Bopa Jean knows his schedule better than he does, and why he thinks his parents are the best grandparents imaginable. You can also learn about the Hereditary Grand Duke favourite bands, why he is so incredibly lucky to live in Luxembourg, that his siblings certainly never were jealous of his future job, how we was brought up and what he wanted to be as a child, that he is going to keep any girlfriend's identity private until an official engagement, and he neither has Lady Gaga's nor the Duke and Duchess of Cambridge's phone number.
* He simply is a bad loser.