I think this is the Thomas Jones you said who had the same birth date:
Thomas Jones born 18 July 1835, baptized in Ebenezer Congregational Church, Bangor, Wales, parents William, a mason, and Elizabeth, of Twigwign.
This Thomas had a sister Jane born 12 May 1833.
Have you found this family afterward? Did Thomas survive childhood? And if he was in Wales in 1861, then he is obviously not the Thomas in Johnstown. Unfortunately for us, his father, being a mason, was probably in a better position to move around than a farmer.
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I didn't find Hannah Jones, b 1845 Wales, anywhere else except with Thomas in 1860 in Johnstown.
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I searched the online text of the Biographical and Portrait Cyclopedia of Cambria County, and the History of Cambria County, hoping to find someone from Carnarvon or Bangor. There were many Jones and many people from Wales, but I didn't find a reference to Carnarvon or Bangor. I was looking for someone whom Thomas might have known from Wales. People often migrated to where they knew someone from back home.
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Thomas' obituary did not say much. Attached.
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That is about all I can think of. There was a similar thread on the US board recently, and in the end I suggested the person start with his family and try to work toward the US family. Can you connect your family to the Thomas born in Twigwign in 1835, for example.