There were apparently two contemporary Sarah Fosters in the Andover, Mass. area and both had families.
A Sarah Foster married Benjamin Johnson 2 Jul 1713 in Andover and had a son Benjamin born there 5 Jul 1715.This Sarah apparently died before 1723 (need source for this record).
A Sarah Foster married William Blunt abt 1698 and had 8 children born between 1699 - 1720. This Sarah died in Andover 6 Dec 1760, aged 84.
It is clear these two Sarahs must be different individuals.