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POSEY, JOHN, SENR., Charles County, 6 Jan 1759; 17 Feb 1759
To son Humphrey Posey, use of all that; tract called "Hopewell" In Charles Co. and after his death to my son Edward Posey and after his decease to my son Rhoda [sic] Posey and after his decease to son Walter Posey and after to dau. Mary and after her decease to dau. Vinefutt (Winifred)Posey.
To son Thomas Posey, wearing apparel.
To dau. Lydia Stewart. 1 sh.
To wife Elizabeth Posey use of all my personal estate then to be divided amongst my five youngest children.
To dau. Francis Madox 1 sh.
To son John Posey, 1 sh.
Wife, extx
Wit: Francis Dunnington, John Elgin, John Posey, junior, 30.641
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Name: Steve Norris
Email: keynorris@msn.com
Mary Posey inherited residual rights to the tract "Hopewell" from her father, John Posey. In 1778, as Mary Whaling, wife of Jeremiah Whaling, she sold her rights to Pryor Posey. Please see below --

(Chas. Co. Deeds, V3.295)
Instrument dated 24 August 1778 -- From Rhody Posey, Jeremiah Whaling and Mary Whaling his wife, all of Chas. County, and Thomas Parsons and Winifred Parsons his wife, of Prince William County, Virginia, Planters, to Pryor Posey of Chas. County, Planter, for the sum of £30 current money of Maryland, all that tract of land called "Hopewell" now in the possession of Humphrey Posey Sr., father of the said Pryor Posey, containing 80 ac. Metes and bounds shown in deed.

--sg:
Rhody Posey, his mark "X"
Jeremiah Whaling, his mark "X"
Mary Whaling, her mark "="
Thomas Parsons, his mark "L"
Winifred Parsons, her mark "H"
--Wit: Warren Dent, Will. Harrison
--Ack: by Rhody Posey, Jeremiah Whaling, Thomas Parsons, 24 Aug 1778
--Mary Whaling and Winifred Parsons released rights, 24 Aug 1778
--Recorded at the request of Pryor Posey, 5 Sept 1778

I found no indication that Edward and Walter Posey ever sold their residual rights to "Hopewell". From this, it seems likely that both were dead before the 1778 deed was signed.
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Charles County Land Records 1775-1782; Liber V#3; Page 295, Aug 24, 1778 from Rhody Posey, Jeremiah Whaland (Whaling), and Mary, his wife, of CC, and Thomas Parsons and Winifred, his wife, of Prince William County, Virginia, planters, to Pryor Posey of CC, for 30 £ and for divers other good reasons, all that tract of land called Hopewell (now in possession of Humphrey Posey Sr, father of sd Pryor Posey) lying in CC, hounded by a branch of the Great Dam, containing and laid out for about 80 acres. Signed - Thomas. (I- his mark) Parsons, Winifret (H her mark) Parsons, Rhody (X his mark) Posey, Jeremiah (X his mark) Whailing, Mary (- her mark) Whailing. Wit - Warren Dent, Will Harrison (CC JPs). Afd Mary and Winifret acknowledged their right to the abovesd land. Recorded Sep 5, 1778.