One site on the internet that has the Tuthill family tree says Polly was born significantly later and had only 1 child see the following:
Maria (Polly) Symmes was born on 30 Aug 1767
Children were: John Cleves Short.

(Maria) dau. of John Cleves SYMMES, of New Jersey and Ohio, a descendant of Rev. Zachariah SYMMES, who came over in the Griffin, landing in Boston in 1634. His wife, Anna Tuthill, who d. 1776, was the mother of Maria SYMMES, who m. Peyton SHORT. Her ancestry goes back to Egbert, first King of the English, through Joan GRAFTON, who m. her ancestor Richard TUTHILL, son of William TOTTYL, Sheriff of Devonshire, 1549, and Mayor of Exeter, 1552.