At least two artists use this name:
1) Willem is a Dutch rapper and TMF VJ. Together with Big2 (Twan) he forms the Dutch HipHop duo The Opposites.
2) Willem Verstraaten is a 20 year old singer from Geldrop (The Netherlands).
He participated in the second edition of the Dutch 'So You Wannabe a Popstar'. During the program, he became very popular among the female fans, however he did not win the program, but became third after Tessa and Maaike.