I believe the 3 siblings in this instance are all of Prince George County, children of Francis and Elizabeth Poythress.
The siblings in question:Francis Poythress, circuit rider, d. unmarried at home of his sister Susanna Pryor.Shows in 1810 census in HH of Susanna Pryor as "male over 45" although this could possibily be Mr. Pryor himself.
Susanna Poythress Pryor, b. VA 1747, d. 25 Jan 1817, Mercer County, KY.Shows in 1810 census with 25 slaves.
Elizabeth Poythress Peniston, b. VA, m. Anthony Peniston b. PG County 1741, d. 1793 Jessamine County.Shows 13 slaves in 1810 census.The Peniston line is extensive in Kentucky. Son John Peniston m. Rebecca Nuttall abt 1801.Son Francis Poythress Peniston m. Hannah Satterwhite Moore.Son Thomas Peniston m. Sarah Masterson Dec 1804.Son Samuel Peniston was sent back to VA in 1802 by his mother, apparently to recover dower rights to property husband Anthony had sold without securing.
The line goes back as follows: Father: Francis Poythress, R. S., m. Elizabeth _______ Father: Robert Poythress, (1690-1745) m. Elizabeth _________ Father: John Poythress, d. 1712, m. Christian Peebles Father: Francis Poythress, Captain (the immigrant)b. 1609 Newent,Glos. Burgess for Charles City County and Northumberland County, d. about 1650 Northumberland County.
This Francis line is not to be confused with the line of Lt. Wm. Poythress whose heirs attempted to secure his 4000 acres of bounty land in KY which is registered on KY Sec of State webpage.
Contact me if you wish.My take on this line is in some instances tentative.