Prince Wolfgang of Hesse-Kassel was the designated Hereditary Prince of the monarchy of Finland, and as such, already called the Crown Prince of Finland officially until 14 December 1918, and also afterwards by some monarchists.
Wolfgang was born... Wikipedia
Born: November 6, 1896, Château de Rumpenheim, Offenbach, Germany
Died: July 12, 1989 (age 92 years), Frankfurt, Germany
Grandchildren: Irina Verena Prinzessin von Hessen-Kassel and Christoph Prinz von Hessen-Kassel
Children: Prince Karl of Hesse
Spouse: Princess Marie Alexandra of Baden (m. 1924–1944)