The Dutch vital records information that I found on your family can be readily accessed. I did find the following:
-Izaak van Kerkvoort, born 5 April 1824 in Zaamslag, Province of Zeeland, the Netherlands.
-Cornelia van den Berge, born 11 November 1828 in Zaamslag, Province of Zeeland, the Netherlands.
*You see their marriage info in my previous post**
-Izaak van Kerkvoort, born 21 July 1854 in Zaamslag, Province of Zeeland, the Netherlands.
-Dingetje (Dena) van Kerkvoort, born 2 Ocotber 1861 in Zaamslag, Province of Zeeland, the Netherlands.
I know they emigrated in 1869 and the reason, listed by Dutch records, was for economic improvement. The families social class at the time of leaving the Netherlands was listed as "less well to do". Izaak was a tailor and while he probably did not make a lot of money he was better than some emigrants who were listed as "indigent". His religion was "Christian Reformed" which was a denomination that started with a split in 1834 from the Dutch Reformed Church which was the recognized "State Church". This split was very contentious but it had somewhat tempered by the time the van Kerkvoort family emigrated to America.
I am still looking for the ship that they came on. Izaak's brother Jan, who came in 1855, came on a 3-4 masted sail ship, the "Caroline" (then known as a "bark" or "barque"). I'm not sure that steam-powered ships were up and running in 1869.
Izaak and his wife Cornelia has several other children born to them in the Netherlands but all of them died (2 girls within 3 days of each other). So, only Izaak (Jr.) and Dingetje (Dena) emigrated with them.