Land Deed Mentioning Old John McElrath of Rowan and Iredell Cos., NC

To those who may be interested, below is an abstract of the land deed I mentioned in my original post.From Deed Book 30, pp. 672-4, Register of Deeds for Rowan Co., NC; transcribed in The Burke Journal, Aug 1994 by John H. Smith.

My question to McElrath researchers is, when the deed says "their grandfather John McElrath", who among those mentioned in the deed are "they"?It sounds to me like Elizabeth was a McElrath by birth, and perhaps Robert was her brother.Were they both children of Thomas McElrath?Any help would be appreciated.

"This indenture made [25 Apr 1815] between George & Elizabeth Derreberry of [Burke Co., NC] of the one part and Robert McElrath of [same place] of the other part.Witnesseth that the said George and Elizabeth Derribery for and in consideration of fifty Pounds the said Derrebery doth hereby acknowledge hath given granted bargained an sold and aliened & confirmed and by these presents doth give grant bargain and sell alien and confirm to the said Robt McElrath his heirs & forever all that tract of Land a undivided fifth part of Land situate lying and being in the County of Iredell or Rowan, NC.[60 acres/5 bordering McHenry, Allison, Steele.Also 75 acres/7 bordering Morrison, Hemphill, Brandon] - lade off for Thomas McElrath ars [sic] the Land of their Grand Father John McElrath, and all the wood ways waters and watercourses and all and every appurtenance thereto belonging or in any wise appertaining..."

Signed by George and Elizabeth Derrybery, witness J. McDowell.A note in the Burke Journal below says "dower relinquishment of Elizabeth Derrebery taken by James Marlin, Jr. JSCL&E of the Burke County Superior Court, 30 Oct 1829.Also in Burke Co., John E. Butler appeared the same day before Judge James Marlin and swore that John McDowell, the subscribing witness was dead but verified his signature to the court."