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He was the son of W. D. Caroe and brother of Sir Olaf Caroe. He married Gwendolen Mary Bragg (1907-1982), daughter of William Henry Bragg. His son, with whom he worked, was Martin Caroe. His daughter, Lucy Caroe, historical geographer, married Richard Adrian, 2nd Baron Adrian. He was awarded an OBE in the 1987 Birthday Honours.
- South extension to University of Wales Building, Cardiff (1954) - his father had designed the main building in 1903.