Personally, I think the odds are against Sion Hill being the husband of Elizabeth Marriott.We have at least two competing possibilities for Elizabeth Hill's husband.
Sometime in the mid-1680s, Luke Mizell (born 1660/1) married a woman named Elizabeth.He was living on land adjoining Matthias Marriott at the time.Luke Mizell died in 1693 and his widow remarried by early 1694 to Robert Hill, the uncle of your Sion Hill.They were still living in Surry at the will date of Matthias Marriott.So the "Elizabeth Hill" named in the 1701 will of Matthias Marriott could easily be that person.
In fact, it makes sense.We know that Alice Warren was born about 1645 (from her deposition that she was 32 in 1677) and was already married to Matthias Marriott in 1670 when they settled a dispute over her fathers's estate. Itseems reasonable to me that her children would more likely have been born in the 1670s than in the late 1680s.By 1680 Alice was 35, married at least ten years, and more than likely had already had the three children named in the will.
In addition, I would note that the other daughter named in the Marriott will, Margaret Flake, was married to a man born ca1660 and was already a grandmother by the time Matthias Mariott made his will.
It seems much more likely that Elizabeth Hill was the wife of Robert Hill than of Sion Hill.Sion Hill wasn't nearly old enough to have married a daughter of Mathias Marriott.Sion Hill (Jr.)wasn't born until late 1680 or early 1681.
This was published somewhere in a book, but the author has since recanted.I don't think he looked closely at who Robert Hill's wife was.Most of the attention has gone toward the family of Sion Hill Sr. and not to his younger brother Robert.