Robin & Caroline Adair's (nee Keppel) son was Sir Robert Adair 1763-1855. Details may be found in "Dictionary of National Biography" 1882, reprinted 1950. Also obituary in "Gentlemen's Magazine" Nov. 1855.He married 1805 Mdlle. Angelique Gabrielle, daughter of the Marquess d' Hazincourt and the Comtesse de Champagne. Sir Robert Adair sat in parliament for the whig boroughs of Appleby and Camelford, England.In 1828 his diplomatic services were recognised by his admission to the privy council. He was appointed G.C.B. (civil) in 1831, and the success of his mission was further rewarded by the grant of the highest pension which could be awarded him. He was mentioned in Lord John Russell's Memorials and Correspondence of C.J. Fox, vol. ii. appendix.They were relatives of Lady Caroline Keppel whose mother was a Lennox.Lady Caroline died after nursing her dying sister, Lady Tavistock (Russell). Appears to me as if Caroline may have caught her sister's sickness. It may be worth trying to find your Robert Adair through the Sir John Sidney connections, perhaps may be with the Wyndham - Quin family in Limerick who sometimes called themselves "Lord Adair".