The Cumberland Three
The Cumberland Three were Alex Beaton, Brian Fogarty and Leonard Sturrock, who went the the same school in Glasgow, where they formed a skiffle group.
After school Brian and Leonard sang in clubs together, but it wasn't till they met a German student who ran a folk club in Germany that they were converted to folk music. They reunited with Alex and formed the group.
By 1963 they had a residency at Glasgow's top jazz club, The Royal Garden, alternating with Josh McRae. The same year they appeared with Robin Hall & Jimmie MacGregor at a big folk concert in Glasgow, followed by radio spots and club engagements. Later in 1963 the group moved to London to try their hands outside of Scotland. The group broke up in 1965 and Brian and Leonard decided to give up their music careers.
In 1968 Alex Beaton launched a solo career, singing country and pop as well as folk songs. Eventually he settled on singing "traditional Celtic music", and he now has a large American following, and regularly sells out his tours when he comes home to Scotland. Visit Alex's web site at www.alexbeaton.com.
I haven't been able to trace the others. Any more info, email me.