Isabella Burn's signature from an Indenture made on 23 July 1832 with John Grey of Milfield Hill. This document mentions a Bond made by Adam Sibbitt of Ancroft ?Greens, Patrick Dickson of Berwick upon Tweed , and James Thompson, farmer of Shoreswood Red House, dated 16 December 1800, for £1,600. A promissory note from Alexander Hogg of Edington Mill, Berwick, miller, for £200, and a note from John Grey and Robert Johnson of Scremerston , and that John Grey, John Carr and George Carr, as executors of John Carr deceased, late of Ford, promise to pay Isabella £1,200 value from Etal Colliery so that Isabella can make provision for her nieces, Margaretta the wife of Henry Grey minister of the church and parish of St Mary's Edinburgh and Mary Grey Lundie of Kelso, widow and Hannah Cox, wife of John Cox of 16 Waterloo Place, Albany Road, Camberwell, a Captain in the Royal Navy. In Isabella's will her money was divided equally between Margaretta and Mary.
Documents from Milfield Hill , now held at Berwick Archives include a trust for Mary's sister Isabella Burn of Berwick and the will of their father John Burn, merchant of Berwick, who was a cooper, with premises in Bridge Street which he shared with Christopher Mitchelson. John Burn had a friend called George Ramsay who lived in Virginia Street in the City of London. He owned trade shares in ships. His friends were Richard Todd, James Bell and nephew Thomas Gilchrist , all coopers in Berwick. His will was witnessed by Richard Blackett, Samuel Lough and Wm. Graham. No other children are mentioned in his will and Isabella never married. So apart from Mary Burn's children with George Grey these particular Burns have no other descendants.
The family of Mary Burn.
John Burn's signature from his will written on 18 Jan 1793, and proved 17 March 1795. Both signatures from documents at Berwick archives. NRO 496 - Grey of Milfield.
Trumans the brewers best account was said to be "with John Burn and Co. (later Thomas Gilchrist after Burn's death in 1795) of Berwick, 'who deals so largely with us as to be able to supply you on better terms than we can ourselves' " The Brewing Industry in England 1700-1830, published by Cambridge University Press in 1959,p.148, here

Mary Burn of Berwick who married George Grey of West Ord, Sandyhouse and Milfield, in 1782

The farmers at Middle Ord on the 1841 census maybe relatives? From the 1841 census: Alice Burn at Middle Ord aged 50, with John Burn 20, and Mary Burn 17. Presumably this is the same John Burn (Tweedmouth, farmer, Middle Ord, 1848) on the Board of Guardians of Berwick minutes: here.

 

It is possible that the Burn families at Garrettlee and Horsley birks farms buried at Longhorsley may also be connected. 130. Robert BURN died Jan [-- ----] Matthew BURN died March [-- ----] George BURN of Horsley birks father of above sons Died Janr 25 17[--] aged [--] Yrs. John his son died Febr [--] 17[--] aged [--] Yrs. Mary his Wife died Feb [-- ----] aged [-]6 Yrs. 131. The family burial place of John and Margaret BURN of Garretlee. Mary their daughter died June 30th 1805 aged 12 years. Margaret BURN died July 7th 1823 aged 57 years. John BURN died Novr 20th 1830 aged 84 years. Margaret their daughter died July 29th 1847 aged 52 years. George their son died July 15th 1865 aged 66 years. Thomas their son died Decr 22nd 1869 aged 72 years. On back: In memory of Jane wife of Ralph SHANKS who died Decr 15 1871 aged 62 years. Dorothy BURN died June 11 1878 aged 75 years. From Longhorsley's website here.