Attorney. Son of John Carre of West Nisbet, Cavers and Hundolie (d. 1737) and his second wife, "Miss Home", a daughter of Andrew Home of Kimmerghame. One of Ralph's brothers was George Carre of Nisbet (d. 1766) who in 1755 became a Senator of the College of Justice as Lord Nisbet. He was also, through his half-sister Jean, uncle of Agatha Drummond, Lady Kames.
Boswell met Ralph Carre at Kames on October 17, 1762, describing him as "an uncle of my Lady's (Lady Kames), who has been upwards of twenty years an attorney in London: a round man with a bob-wig and his coat buttoned, of manners plain and somewhat vulgar. I am told he is a very worthy man and very active in business. He is also called sensible, but I thought he spoke too much and too minutely, took too much snuff and raised too often a kind of an ale-house laugh".