Wilcke was born on 11 March 1913 at Schrimm in the Province of Posen, part of the Kingdom of Prussia at the time, now Śrem in the Greater Poland Voivodeship, Poland. He was the son of a "Hauptmann" (captain) of "Infanterie-Regiment" 47 (47th Infantry Regiment), Hans Wilcke, who died of pneumonia when Wilcke was just four weeks of age. His mother, Hertha von Schuckmann, married again on 14 June 1919. In 1931, Wilcke was arrested for attending a then-illegal demonstration of the Nazi Party. Although his loyalty to the Nazi cause is emphasized multiple times in his personal military files, according to biographers Prien and Stemmer, he was a firm opponent of the National Socialist regime; later in his career, for a time after taking command of III. "Gruppe" (3rd group) of "Jagdgeschwader" 53 (JG 53—53rd Fighter Wing), he had the Swastikas on his unit's aircraft painted over. He volunteered for military service in the "Reichswehr" after receiving his "Abitur" (diploma). He joined "Artillerie-Regiment" 6 (6th Artillery Regiment) in Minden as a "Fahnenjunker" (officer cadet) on 1 April 1934. His legal guardian and stepfather, Friedrich von Scotti, also served in this regiment.