I would speculate Nancy is the d/o Wm/Mary, since she is living in the same twp. Altho Wm/Mary were m in Belmont Co, I think they may have resided Columbiana Co OH 1830-40.There is a Wm BLACKBURN in Guernsey & Jefferson Cos, but they both too young.
1830 Columbiana Co OH BLACKBURN Wm 40-50; w/30-40; 2f 5-10; 1f 10-15; 1f 20-30 [I don't know who the older females might be unless Wm was m previously] James & Findley b 1830 & 1832.
John 20-30; 1f 60-70 [mom?]
Joseph A 20-30; 1f 5-10; 1f 15-20; 1f 30-40 [wife/ch/minlaw?] all 3 live next door to each other.
Wm and/or Mary BLACKBURN returned to Belmont Co. [he may have d in Columbiana].No early online marriages for Columbiana.
Wm/Nancy CAMPBELL removed to Harrison Co, and I THINK I have the lineage for the CAMPBELL family...beginning with John died 1775 York Co PA; had son John who had son William b 8-11-1779 and m Eleanor? SMITH & removed to Wheeling Twp, Belmont Co OH.[HARRISON CO HISTORY] This matches the 1850 Wheeling, Belmont Co census. If this looks like the right family, I will try to send to you by email, but don't know if my scanner is working.