I found a third child of Mannes Egbertus and Theodora:
Suzanna ten Oever
Born Avereest 11 May 1865 at 05.00 hrs.
She was born in the same year Mannes left for the USA, so likely mom and child stayed behind a little and were planning to come over later.
I don't know what happened to them, because I can't find them anywhere, no deaths, not anything!
I also found the 1870 census on Herman.https://familysearch.org/pal:/MM9.1.1/M626-NS5
No mention of daughter Suzanna
And his marriage to Anna Mary Schulte on 19 Feb 1866https://familysearch.org/pal:/MM9.3.1/TH-1-18059-12587-54?cc...
PS As for your other Dutch line; let's hear it!