It may be possible this William F. Hill is the son of another William, born 1655 in St. Mary's Woolnoth, in London, England, and who emigrated with his siblings in 1677/1678. His sibling names included Robert, Elizabeth and John, names repeated in later generations as well as prior, if this William is correct. This family was from the Devon/Somerset area in England but also lived in or near London in the years leading up to their departure form Europe.
The dates work out to line up with William (1655) arriving in Baltimore, working as an indentured servant for a few years to pay for the voyage, then marrying sometime after completing his time, and having at least one child, named William after himself, and Francis after his grandfather. He is thought to have died in Maryland or Virginia. William F. is born in Caroline County, VA, some 10 or 15 miles from the Maryland border.
Some of William F's descendants also had marriages with families who originated from the same area in England. For these reasons and a few more details I believe this is the likely father of William. The Geni profile of William (b. 1655) is 6000000000967116703, his brother Robert is 6000000000967116788, and their father John Ellis Hill is 6000000018736560611.