Marinus van der Stel - Marinus

Trouwboek Poortvliet 1664 – 1810 afschrift Kloet - DTB 072a (archieftholen.nl) gives: 1721 "geh. 24/10 Marijnus Stellenaer j.m. v. Strienham X Elisabeth Kerkoele j.d. v. Th. o 24/9" ("Stellenaer" is a spelling alternative for "van der Stel"; see his second marriage in 1752 mentioning his first wife).
So Marinus was born in Strijenham, a hamlet on the island of Tholen, Zeeland, NL. (the parents you originally had connected were living at the time in Haarlem, North-Holland, NL; which is a long way away.)
Around the time of Marinus' estimated birth we can find Cornelis Stelle and Adriaentie Mol baptising twins Marijnis and Cornelis Adriaen on 28 August 1695 in Tholen. (Strijenhamd didn't have a church so children were baptised in Tholen or Poortvliet; the baptism records for Poortvliet for this period were destroyed by the fire in the archive in Middelburg in May 1940).

PS I just noticed that I origianally had Hendrik and Cornelis Adriaen as the twins with an estimate for Marinus, but I just looked up the record and I must have switched Hendrik and Marinus by accident. I'll correct that.

Also Marinus has a son Cornelis and children are often called after their grandparents so this matches with Cornelis Stelle as the father of Marinus.
(I haven't found any hard proof, but imho this is the most likely situation).

Thank you sir, I'll make the correction. The -aer in surname suffixes often denote Belgian roots, perhaps Belgian protestants that fled the war going on in the low countries.