Lizzie's birth in Lynn, MA, 1873
https://www.familysearch.org/ark:/61903/1:1:FX4C-S9CThomas' section of the tree at familysearch mentions a sister Nellie, born in 1875 in England
https://www.familysearch.org/tree/person/details/KFLX-7V2Nellie
Birth 30 Aug 1875
18 Adams Place, Southwark, Surrey, England
Death 23 May 1961
Kenley, Surrey, England
That puts the family back in England by August 1875, if correct.
If you click on her on the tree, one of the sources is the 1939 Register of England which, I think, gives the exact dates of birth.
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Regarding citizenship, my guess was that being born in the US would have made the child a citizen. It does now, and it hasn't changed in at least the last 40 years, if ever. And they are tightening the rules lately, not loosening them, so I'd guess it has always been that way. It might even be in the Constitution.
At any rate, Thomas' passport application says he was a natural born citizen of the US, and the form says "for native citizen." Although he does say his father is a native US citizen as well. Probably not, right? But they were probably more interested in Thomas' citizenship than his father's, if they checked it out.
