There is confusion about Gerrit Jansen and his son Guert Gerrits.
Gerrit Jansen marr.1) Unknown
Gerrit Jansen marr. 2) as widower (wife not named) Pietertje Heertjes
The couple made a pre nuptial contract 15 Aug. 1654 (NYGBS record. v. 120 1989)
Pietertje was widow of Claes Jacobsen and had a son Dirck Claesen
Gerrit had children (not named) the contract assured that children will receive their inheritance form their parent.
In September 1655 we have record of "3 children of Corporal Gerrit Jansen van Steenwyck" were removed to Staten Island (Hist. of NN v. 1 by E>B> O'Callaghan) because of the Indian attacks.
These children are likely Geesje Gerrits, brother Guert Gerrits and one unknown child.
Jannetje Gerrits is probably a half sister as she was already married in 1652 (NA DRC)
Guert Gerrits van Zutphen marr. (he later used Steenwyck) marr. 10 Oct. 1664 Lysbeth Cornelis widow Hendricksen.
They had no children
Guert Gerrits and Lysbeth Cornelis make a mutual will in 1688 pr. 27 Apr. 1697 He mentions sister Jannetje Gerrits (her children) and Geesje Gerrits (her children) and a relative of Lysbeth Cornelis.
Lysbeth Cornelis marr. 1) Marcus Pieterse
Lysbeth Cornelis marr. 2) 2 Oct. 1659 "Gerrit" Hendricksen van Harderwyck
Gerrit Hendricksen van Harderwyck marr. 1) Ytie Jans and had children:
Otto Gerrits 1646, Jan Gerrits 1650 and Lysbeth Gerrits 1653 (these children are not "van Steenwyck" of course)
Jannetje Gerrits van Steenwyck marr. 31 Mar. 1652 Caspar Steynwits (NA DRC) He marr. 2) Tryntje Jacobs 15 Mr. 1671
Geesje Gerrits van Steenwyck marr. 14 Jan. 1666 Jan Dirksen Straetmaker
Jan Dirksen Straetmaker marr. 2) Neeltje Buys widow Jacob Vygoor 12 Jan. 1707 in Bergen (Bergen DRC)