John Witcher had a "spinster"daughter marry in 1769 Bedford County, Virginia. That would make John born before 1730.
William Witcher had a land entry in ca 1764 Halifax County, Va, hence liely born before 1743.
Daniel Witcher likewise in 1766, born before 1745.
Another (or the same ?) Daniel went early to Cabell County, Virginia, married Sally Ward. It may be he who was in Montgomery County, Virginia in ca 1782 with Ephraim and another Witcher (James ?). Ephraim went to Surry County, N.Caroklina, near Montgomery.
Only one Daniel appeared in Pittsylvania County records, the one who died in Smith County, Tenn. in 1815, married Susannah Key Dalton. He is said to have been born in 1724.
Pittsylvania was formed in 1766 from Halifax. Bedford was just across the Staunton (Roanoke) River from Pittsylvania. These people lived on or near the Pigg River and likely did not move at all as these new counties were formed.