In doing research on the PROCTOR line I ran into the following which may shed some light on this issue. It is a Genealogy Genforum Posting by Bob BAID from 15 December 2002.
Marriot was alive on 5 March 1672 but dead by 7 May 1672 when appraisers were appointed. A settlement was ordered on 2 September 1673 and an accounting was presented on 21 November 1673 by Nicholas MERRYWETHER as "trustee of ye sd Marriots will". Because the accounting was complicated by numerous small debts and there was "more than ordinary trouble in it", George PROCTOR (who married the widow) was ordered to finish the accounting. The same court appointed PROCTOR and MERRYWETHER as joint guardians of William MARRIOTT, the orphan of William MARRIOTT (implying that William was under 16).
On 7 July 1674 a portion of the estate was awarded to John BISHOP. He was evidently the son of William MARRIOTT's widow (formally the widow of John BISHOP Sr.) per an Orphans Court judgment (which no longer exists). George PROCTOR was again ordered to pay out of the estate to John BISHOP in 1677.
There are two entries in Deed Book 2 regarding this estate. Page 37: On 7 November 1673 an accounting shows payments to William ATKINSON in right of his wife and Mr. SALWAY in as marrying Elizabeth PECK. These women were apparently legatees of the will, but not daughters of William MARRIOTT. Page 323: a 7 November 1682 accounting which shows George PROCTOR paid in right of his wife one-third of the estate, and the rest to Samuel THOMPSON who married the "surviving of ye two orphans" Mary. It would seem William MARRIOTT had two children, William and Mary. William died before 1682 and Mary married Samuel THOMPSON in March 1682 "daughter and heiress of Major William MARRIOTT, of Surry" (Surry Records).
I remain at a loss as to information about the elusive John BISHOP Sr. I do know that in February 1660, 44 year old William MARRIOTT married 19 year old Susanna SWANN. She died "eight months and twenty two days" later, 25 November 1660.
William MARRIOTT died before May 1672, and his widow Elizabeth married George PROCTOR on 4 September 1672. This would mean she married William after the death of his wife Susanna in November of 1660.
William and Mary would have to have been born in, or after, 1657 to have been minor children in 1672. This leaves a question as to the mother. Susanna SWANN died "without issue" and if Elizabeth was the mother why were the children considered orphans? Perhaps there was a different definition of orphan in 17th century Virginia or perhaps William MARRIOTT had a spouse we have yet to uncover.
Hope this is helpful,