Susan, I hope you get this as it does not look like you have posted recently on genforum. I am not sure if you have stopped researching or found what you are looking for. ReReading through your posting, while I am not sure I can help you on the later family, I can perhaps help shed some light on Alexander White's wife.Though I have no proofat this time, I feel she was probably Isabella Craige, dtr of John Craige who d. 1766.
White, John.Admin. of, to Isabella White. Feb. 8, 1786. Arch. vol. A54, page 119. Reg. of Wills, Liber M, folio 95
White, Stephen.Admin. of, to Isabella White. Feb. 8, 1786, D. B. N. Arch. vol. A54, pages 164-165. Reg. of Wills, Liber M, folio 95. Note:—Arch. vol. A54, page 164 mentions heirs, Jacob, William & Isaac White, Sarah Smith (wife of John), William Needles (son of Rachel White), Mary King (wife of William), heirs of John White.
My tree can be viewed on Ancestry. If you are still hunting, I would love to share info.
Also, I did come across a posting -have to find it again of another of the sister's who m. I believe a Hatfield were in ? Chester Co, PA and westward from there.
The John Craige above is a brother to my James who was my xx..GGF.
Thank you so much for pointing me in this direction.