Sieyes: Origins: in Europe
You can find a large pool of persons named Sieyes actually living in Belgium in the late 1600s early 1700s
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Many of them held important positions:
and were well established
Royal Postmasters, Vicars, State Deputies
Its not likely any Sieyes would flee that region due to religion and poverty
but more likely they wished to migrate to England and the USA for profit purposes or to escape something else in their lives.
Otherwise the name is prominent in Provence:
a region not very well represented in migrations to North America or England
Its far more likely Jean voluntarily joined the English navy if that is the case or that he took the voyage and absconded into the woods if he could not pay his fare over at port.