Thomas Johnson marred Sarah Ann Davies in Treorchy in September 1883. The birth of their first child, Robert Richard, was registered in Pontypridd, March quarter, 1884. Born Treorchy. He was still lving with his parents in 1901. He married Mary Jones in March quarter, 1906. Registered in Pontypridd. Thomas and Sarah's 12th and last child was registered in Pontypridd, September quarter, 1909, named Robert Richard. In 1911 RRJ(1884) was living with his wife and RRJ (1909) was recorded with his parents. This family is a twig at the end of a branch of the tree. The only certificate I have is for the marriage of Thomas and Sarah Ann. Can anyone detect a flaw in my reasoning or, alternatively, suggest a possible explanation for the duplication?