Hi Karen, I searched the U.S. Censuses and the earliest mention of the Bell family was in 1860 in Pontotoc, MS. I was hoping to find a Census where the parents were living with Asman and Sarah but didn't find that.
I'd post on the Mississippi Pontotoc County Message Board and ask where can you find marriage certs for that County (assuming they married there). Sometimes parents names are listed on the marriage cert.
Do you know where they were born? The parents names are always on birth certs.