His father was Charles de Nielles the elder, from Tournai, a Reformed minister who worked in Antwerp and Wesel, and ended his life in 1604 at the Walloon church in Hanau.
[1][2] The son was born at Wesel,[3] and came in 1604 from Cologne to Utrecht as a preacher to the Walloon congregation, on the invitation of Anthoine L'Empereur.
[4] Niellius was one of the Remonstrants summoned to the 1618 Synod of Dort (Dordrecht), set up to decide on the divisive theological issues in the Dutch Reformed Church.
[13] The other six released with Niellius were: Theodorus Boomius (Dirk Boom), Simon Lucae Bysterus, Petrus Cupus, Arnoldus Geesteranus, Paulus Lindenius, and Bernardus Vezekius.
[15] He translated into French as Balance pour peser en toute équité the anonymous pamphlet in Dutch Weegh-Schael (1617, by Jacobus Taurinus).