Hello RuthieB,
I was there end of July, part holiday, great to look up, and so friendly, stopping people on the road who knew my grandfather (son of Elizabeth or one of the many kids - Thomas Davies).
Anyway, the Drummonds are I think from Edwinsford. They were about, like the Johnes, in the 1800's. The relative in question was Oswyn. I believe his full name may be Thomas Oswyn Evans. His mother was a daughter of Elizabeth, her name also Elizabeth but known as 'Bess'. She married a Thomas Evans. All from Caio. Anyway, the family apparently lived at The Lodge wherever that is in Caio, near the Dolaucothi Mines, I think Dolauchothi Lodge. Bess was a cook at the mansion and their son Oswyn was much favoured by the mansion - benig sent away to public school and Lampeter Uni being paid by them. He died in the 1940's and was an DFC Air pilot.