I don't know if it's same-name mix-ups, but trees on Ancesty states specifically that this Mary's father is NOT the Cannon Cumbo whose father was Gideon Cumbo. The ones I've seen show this:
Mary Polly Cumbo
BIRTH: 1775 Bladen, North Carolina, United States
DEATH: Apr 1850 Robeson, North Carolina, USA
sources (3)records (2)
Father: Cannon (not to be confused with Gideon’s son Cannon b. 1735 Cumbo (Cambow) (1730–1817)
Mother: Elizabeth "Ally" Cumbo (Cumbaa) (1730–1808)
Spouse: John Thomas Cumbo (1773–1814)
Married 1794
Children:
Abby (1800–1878)
Britton (1800–1899)
George Allen (1805–1884)
They have Mary married to John Thomas Cumbo (1771–1797) and their this Abby as their daughter.
If anyone has documentation for either set of parents, any help would be appreciated.
Thanks.