Re: the Dunbar-Nasmiths-
David Arthur Dunbar-Nasmith was s. of Adm. Martin Eric Dunbar-Nasmith (1883-1965), R.N., V.C., K.C.B., K.C.M.G., flag officer in charge, London 1942-5, and in retirement vice-chairman of the Imperial War Graves Commission, Vice-Admiral of the United Kingdom, and president of the Royal Naval Benevolent Trust. Although born at Barnes, Surrey (now Richmond upon Thames), he lived at Glen of Rothes, Rothes, Morayshire. Having in 1920 married Beatrix Justina (1897-1962), C.B.E., D.StJ., dau. of Cmdr Harry Dunbar-Dunbar-Rivers (1857-1911), of Glen of Rothes, R.N., J.P., he adopted the additional name of Dunbar in 1923. Beatrix was apparently 'a descendant of the shipping magnate Duncan Dunbar' (according to 'On Courage: Stories of Victoria Cross and George Cross Holders', by The Sebastopol Project, 2018), with the adoption of the Dunbar name being for inheritance purposes (as one would likely have concluded). Presumably the 'shipping magnate' Duncan Dunbar is this man:
https://en.wikipedia.org/wiki/Duncan_Dunbar_(junior) [son of another Duncan Dunbar (1764-1825), of Limehouse, London, a brewer and wine merchant]. Harry Dunbar-Dunbar-Rivers appears (as per 'Journals of the House of Lords', vol. 137, 1905) to have been originally Harry Rivers; that same source mentions the 1848 marriage of Captain Edward Dunbar, 22nd Regiment of Foot, and 'the late Mrs Phoebe Dunbar or Dunbar Dunbar, of Sea Park, in the county of Elgin', and a 'Reverend John Archibald Dunbar Dunbar' also of Sea Park.
EDIT: BP 2003 has 'Edward Dunbar-Dunbar, D.L., J.P.' as s. of Sir Archibald Dunbar, 6th [not 5th] Bt; the Rev. John Archibald mentioned above was his son. Phoebe Dunbar was, as indicated above, dau. of Duncan Dunbar (senior) and Phoebe (née Bailey).
Had I a little more time, I would take a look at the Nasmiths (at one time evidently of Barnes), but can't do so right now.