Nancy, your William was the son of John Gregg and Elizabeth Cooke. He married Margery Hinkey at Centre Friends meeting 7/29/1725 and they had six children: Elizabeth, Harmon, William, Joshua, Hannah and Margery. His wife Margery died about 1740 and William remarried about 1742 to Ann Warmsley, having one son, Abraham.
The Greggs are one of my direct lines, so I've collected a good bit about them over the years!
To see a map of the New Castle county Hundreds, take a look here: