I see that the only source cited for this line of descent is Ancestry.com. That's usually a bad sign when no more-specific sources are given and, sure enough, it looks as though in addition to the date problem there may be a joining of two unrelated lines of descent.
According to Find A Grave (not always a reliable source, either) William Boggs (1716-1790) was a son of James Boggs (1667-1736) and Rebecca Moray (c1675-1720). The Find A Grave entry does include an excerpt from the abstract of William's will, which gives his children as Joseph, Jane, Elizabeth, Rebecca, James, Robert, Margaret and William.