Brab C was George's son...
George requested the use of Family Crest as a direct descendant, so had to lodge paperwork of lineage which confirmed he was entitled to use it.
So, he is the son of...., who was the son of..... etc. etc
NLI is providing you with a copy of the Grant of Arms involving Eccleston and Sheils.... wait and see how far it goes back on Shiels!
Then chase George if needed.
You have Tabular pedigree of the descendants of Sir Edward Brabazon, baron of Ardee, 1549-1891; 19th c. Collection: MacIomhair Papers Dublin: National Library of Ireland, Ms. 24,017
Pedigree of Brabazon of Eastwell in Co. Leicestershire, Barons of Ardee, Earls of Meath, of Ballinasloe, and New Park, Co. Mayo, c.1066 -- 1829. Dublin: National Library of Ireland, Genealogical Office: Ms.168, pp.396-405
Copy of confirmation of arms to the descendants of the Rev. Brabazon Disney, D. D., Rector of Kilmore, Diocese of Armagh and to his grandson, the Very Rev. Brabazon William Disney, Dean of Armagh, son of Rev. Brabazon Disney, Rector of Slane in Co. Meath, May 25, 1861.
Dublin: National Library of Ireland, Genealogical Office: Ms.108, pp.370-1
The Pedigree of Ecclestons has been done and is at Trinity College. all entwined with each other!
See if Sheils are mentioned in any of them??