Janssen was born in Düsseldorf, son of the engraver Tamme Weyert Theodor Janssen [de] (1817–1894), by whom he was first instructed before studying at the Kunstakademie Düsseldorf under Karl Ferdinand Sohn and Eduard Bendemann.
Peter Janssens (17 June 1934 – 24 December 1998) was a German musician and composer who wrote and performed incidental music for several theatres, and songs and musicals of the genre Neues Geistliches Lied, a pioneer of Sacropop [de].
Jann-Peter Janssen (12 February 1945 – 7 December 2022) was a German politician. A member of the Social Democratic Party, he served in the Bundestag from 1994 to 2005. [1 ]