I thought that Thomas Custis and Ann Keady (Cady) Custis might be parents of Ann Custis who married David Dunn in 1782 Craven (assuming she was born c1762).I thought Thomas might be a son of Henry.Peter Custis may be another child of Thomas (grandson of Henry).
When I saw Peter Custis as the bondsman for William Dunn's marriage (William was David's brother), that supported the Dunn connection and connection to Ann Custis (assuming she was the daughter of Thomas and Ann Keady Custis).An "AnnCady" Custis married in 1799 to a Mumsford in Craven, suggesting this was a second marriage.
It seems there was only one Custis family in Craven NC in the 1770-1790 timeframe and that Ann and Peter are related.
I haven't researched this other than basing it on other findings and family trees.
I would like a copy of the will if you can send it.That might provide some answers.