Iron Fist could be called 'the birth of Helloween'. Since it was formed by Kai Hansen, Ingo Schwichtenberg, Markus Grosskopf, and later joined by Michael Weikath, all were from lineup of the early years of Helloween. Here's some info concerning Iron Fist and the beginning of Helloween.
"The history of Helloween begins in 1978, when Kai Hansen (vocals/guitar) and Piet Sielck (vocals/guitar) are playing in a band called "Gentry" in Hamburg. Until 1981, Gentry changes it’s moniker to ”Second Hell”, which then features Markus Großkopf (ex-Traumschiff) on bass and Ingo Schwichtenberg on drums. After Sielck leaves Second Hell to become a sound engineer, the band again changes to "Iron Fist". In 1982 Michael Weikath, guitarist of the local band "Powerfool", tries to lure Kai into his band, but then decides to join Iron Fist instead. In 1984, the small record-company Noise invites the band to contribute songs to the compilation "Death Metal". Still not satisfied with their outfit, Iron Fist again change to "Helloween", a name which Ingo Schwichtenberg comes up with, along with the ideas to replace the ”o” with a pumpkin and to draw pumpkin-projects for specific songs, which will later become a trademark of Helloween." From the Helloween official site.