Individual Details

https://archive.org/details/historyoftownofh00cogs/page/438

There could be two younger children, Mary Ann and Timothy. Mary Ann would have married Sylvanus Brown
I am going to add them to see what happens
Mary Ann may well be true because Jane Abbott (Mary's single sister) was living with Sylvannus and Mary Ann Brown in 1850 in Waterbury Vermont
And Timothy also as his death record gives names of parents

Birth	15 Oct 1762	Wilton, Hillsborough, New Hampshire
Marriage	Abt 1787	Sarah Smith
Death	8 Sep 1831	Thetford, Orange, Vermont

Spouse	Sarah Smith (1765 - 1848)
Child	James Abbott (1788 - 1870)
Child	Daniel Abbott (1790 - 1872)
Child	Nathan Abbott (1791 - )
Child	Seba Abbott (1794 - )
Child	Sally Abbott (1796 - 1867)
Child	Jane "Jennie" Abbott (1798 - 1867)
Child	Appleton Abbott (1800 - 1864)
Child	Jonas Abbott (1802 - 1875)
Child	Timothy Abbott (1806 - 1871)
Child	Mary Ann Abbott (1809 - 1884)

Father	Nathan Abbott (1728 - )
Mother	Jane Paul ( - 1772)
Sibling	Paul Abbott (1759 - )
Sibling	Nathan Abbott (1761 - 1767)
Sibling	Asa Abbott (1765 - 1852)
Sibling	Nathan Abbott (1767 - )
Sibling	Mary "Polly" Abbott (1769 - )
Sibling	Martha "Patty" Abbott (1771 - )