For anyone else that is interested in this family and may see these notes, I now have the marriage certificate in Wales for Alexander Mackay and Catherine Rowlands in 1886.The cert states David as being Alexander's father ("deceased" and he died in 1880), Joseph as being Catheine's father and I have since found out that her mothers name was Elizabeth and her sister, Mary Ann, was also a witness to the marriage. John, Alexander's brother, was also a witness to the marriage