In an age of religion, D. A. Thomas was that rarity, a man honestly uninterested in religion. That said, Thomas does not appear to have been an atheist, but to have found the religious sectarianism that marked the life of Wales at that time distasteful. Although brought up a Baptist (and later Congregationalist), he was received into the Anglican Church upon his marriage to Sybil Margaret Haig in 1882 and was baptised at St. Andrew's Church, near Barry. The wedding took place in a billiard-room at her parents' house. A daughter, Margaret, was born in 1883, the only issue to the couple.