Re: Christian Plopper's in New York and Wis.
I have just found what I think is a line of Ploppers in my tree which, coincidentally, appears to be what you have outlined here . .except that the children listed I found are not the same as what you have. I'll walk through this and see if we can sort it out.
I began with a search for James Henry Waite (b. 9-6-1832 NY, d.4-17-1905 WY)and his 1st wife "Julia." This all came from a lengthy family paper with no other information on Julia other than she died in 1874, the same year as their youngest child Rasce.
So in trying to find record for this Julia, I found a marriagerecord in Sheboygan WI (where the first 3 of their kids were born) for James Wait & Julia Plafoer. One of the kids' later marriages lists their mom as Julia Plupper. (This Julia Plupper enrty lists her parents as Hery & Margarett Pluppe.)
So in doing some searching I found a Julia Plopper who seems to fit everything nearly perfectly. For instance:
1850 Census Holland Sheboygan Wisconsin
Henry Plopper 64 NY
Margaret Plopper 53 NY
Charles Plopper 14 NY
Julia Plopper 12 NY
Maria Plopper 10 NY
That doesn't seem to be the same group of children you listed, although Henry & Margaret match identically. It doesn't list relationships at all. I notice looking at the scan, the next entry is for a John Plopper aged 33 with his wife Louiza and their children.
Is it possible that Charles, Julia, and Maria are grandchildren of Henry & Margaret rather than children? Maybe they didn't even know?
I had found the death record for the Stephen you list and was thinking he was an older brother of Julia (him 1820, her 1838)
I dunno, maybe I'm on completely the wrong track. Everythingseems to point this direction but something isn't adding up right.