You're in luck.

Castles of Aberdeenshire by Sir Andrew Leith Hay published at Aberdeen by D. Wyllie & son 1887 page 21
"The lands of Barra, or Barracht, belonged before the middle of the thirteenth century to the family of King, afterwards of Dudwick in Ellon. More than two centuries later , in 1476, James King, "in Barracht" and Alexander Seton "in Meldrum" are among the big lairds and quiet neighbours of Inverurie"
The book then continues with a one page potted summary of the King family as they are mentioned in various legal documents.
I strongly suspect the documents themselves are those which have been published by the Spalding club as part of a 4 volume work but note these are in the original latin.
Regarding a link between that King family and advocates by the name of King in Edinburgh...
The Blackhalls of that ilk and Barra, hereditary coroners and foresters of the Garioch. Alexander Morison published in Aberdeen printed for the New Spalding Club 1905
page 51
"Lastly there was a bond signed on Feb 8th, 1590-91 (Reg. Sec. Sig., 1590-91 p581-582) for Alexander Seton of Meldrum and others, including William Strachan, apparent of Tippertie, and for many other Setons, that William King of Barrach, James King burgess of Aberdeen; Alexander King, Advocate in Edinburgh, and Elizabeth Gray, relict of James King, portioner of Barra, should not be molested by the persons named."
This book makes further mention of the King family as they were the prior owners of land as you already know.
I'm not exactly sure if it fits or not but there's an entry in the Index to the register of Sasines for Aberdeen that mentions a Jean King who was the widow of an Alexander Blackhall so the two families may have been related by marriage.
There's also an interesting offshoot, in terms of later descendants, who fought alongside Charles the first in the English Civil War (amongst others).
S_L