His father, born in Semarang on Java, is an Indo (Dutch-Indonesian), who went to the Netherlands in 1932 after finishing his study at the Batavia HBS to continue his higher education there. Once Nazi Germany invaded the Netherlands his father was involved in the Dutch resistance movement, until he was captured and interned in a German concentration camp. After the war he became one of the few Indo advocates for an independent Indonesia. In his view the principle of liberty and independence applied to both situations: Dutch independence from Nazi Germany and Indonesian independence from the colonial Netherlands.
Much of the literary work of the author Jansz is based on his Indo identity and his fathers' heritage.
In 1997 Jansz married actress Jaloe Maat, the mother of his two youngest children. He has a (step)daughter from a previous marriage. He currently lives with his family in Neerkant, the Netherlands.
Together with Henny Vrienten, Jansz wrote the majority of the Doe Maar-songs. Usually they were sung by the one who wrote it (in other words Jansz and Vrienten split the lead vocals). He was originally asked to be the band's keyboardist, and played synthesizer on many songs. His Indo background has influenced much of his work. This is especially true of the Doe Maar song "Rumah Saya" (My House or My Home), where he describes fitting in with neither Dutch nor Indonesian culture fully. This song is featured on one of the best sold albums in Dutch pop history.
No mountains at the horizon, in this land of my birth. [...] And then I long for the land of my father. But also there I will be a stranger. [...] Rumah saya dimana? (Wheres my home?) Song lyrics by Ernst Jansz, 1981.
After Doe Maar broke up, Ernst Jansz did various solo projects, and played in bands such as Dutch folk band CCC inc (where he began his career). Since the mid-Nineties he's a member of singer-/songwriter Boudewijn de Groot's backing band; as with CCC Inc. and Doe Maar he's given the opportunity to express his musical versatility.
Books & albums
Ernst Jansz has written three semi-autobiographical books: Gideons droom (Gideon's Dream, 1983) De Overkant (The Other Side, 1985), and Molenbeekstraat (Een liefdeslied 1948 - 1970) (Molenbeekstraat: a lovesong 1948-1970), 2006). The latter two share their titles with Jansz' solo-albums. Gideons droom is about a second-generation Indo (Indo-European) Dutchman like himself; De Overkant is a three-part book dealing with letters between Jansz and his family (especially his father), the life of his mother, and an account of his trip to Indonesia. Molenbeekstraat covers his early life and mixes in songtext from the Molenbeekstraat album. 
- 1983 - Gideons Droom (novel)
- 1985 - De Overkant (novel)
- 2006 - Molenbeekstraat (novel)