You might be surprised at some of these other families that are connected to the Alexanders in the Cumberland County Wills:
McCAMEY, JOHN, Letterkenny, tanner. 4 Mar 1765-26 May 1766.
Wife Margaret. Sons Robert, John and James. Dau. Mary Stockdale. Dau. Jane McCamey. Dau. MARGARET ALEXANDER, plantation in North Carolina in Sugar Creek Settlement, adjoining James Norris and James Campbell. Daus. Ester Remix and Martha McCamey. Exs: wife Margaret and son Robert McCamey. Wit: Robert McConnell, Joseph Culbertson, Alexr. McConnell. A. 143-45.
PORTER, ALEXANDER, Hopewell, jobber. 2 Mar 1771-25 Mar 1771.
Father Hugh Porter, if alive in the Kingdom of Ireland, County of Down. Land in Ligonier settlement, adjoining land of Samuel Smith, John McMullan and James McCardy. Four youngest bros., William, Hugh, Robert and Joseph.
Bro. James. Sister Margret, married to SAMUEL ALEXANDER.
Exs: John Montgomery and Joseph Bready. Wit: James McKee, John McKee. B. 86.
REED, ROBERT, Middleton, yeoman. 18 Feb 1772- 2 Nov 1772.
Wife Elizabeth. Oldest son James. Son-in-law James ALEXANDER and Rose his wife. Dau. Margret. John McDowl and Elizabeth his wife. Daus. Mary and Christian. Exs: wife Elizabeth and Jonathan Kearsley of Carlisle. Wit: George Duffield, Richard Rankin, John McClure. B. 138-140.
REED, ROBERT, Middleton, yeoman. 8 Feb 1772 - 2 Nov 1772.
Wife Elizabeth. Oldest son James. Son-in-law JAMES ALEXANDER and Rose his wife. Dau. Margret. John McDowl and Elizabeth his wife. Daus. Mary and Christian. Exs: wife Elizabeth and Jonathan Kearsley of Carlisle. Wit: George Duffield, Richard Rankin, John McClure. B. 138-140.
ROSS, ELIZABETH, Carlisle. 21 Sept 1773 - 19 Dec 1774. Grandson James Mitchel. Grandson, Ross Mitchell and his dau. Mary Mitchel. Granddau. Elizabeth Holt, wife of Thomas Holt. Elizabeth, youngest dau. of said Thos. and Elizabeth Holt. Other children of said Thos. and Elizabeth. Granddau. Eleanor Cunningham, wife of Henry Cunningham and their children. Granddau. ANNE ALEXANDER, wife of THOMAS ALEXANDER. Exs: Thomas Holt, Saml. Laird and Wm. Lyon, Esq. Wit: John Davis, John McKee, Ephm. Steel. B. 183.
I'm sure there are more, this is just all I've come across so far. If you have others, please post them.