This might help: George Abbot immigrated to the U.S. (1644) had a son George Abbot (b. 1632) he had a son George Abbot (b. 1659) he had a son Moses Abbot (b. 1699) he had a son Aaron Abbot (b. 1746) he had a son Sewall Abbot (b. 1768) Sewall and his wife Dorothy (House) had 8 children, all of which had one "t" on the end of the last name, with the exception of their 6th child, John Sewall Abbott (b. 1800) I also am a descendant of George Abbot, and all of the above mentioned are in my lineage as well, hence my last name having 2 t's John Sewall Abbott is the first ancestor with the 2 t's, and each of the following generations stemming from John Sewall Abbott have had 2 t's.There is no nationality difference, just a bit of a change to John's name.I hope this helps!