Mark Is it your grandfather or Patrick O'Donnell who was the national school teacher? Did you check on O'Donnell /Shiel marriages OUTSIDE of Galway? I have a feeling that some National school teachers were sent on postings. Many of the ones I have come across in the 1901 and 1911 censuses gave their place of birth as a different county to where they were working. I don't know how widespread a practice it was. I had a look for Sheil/Shiel etc in Griffiths c 1855 - much too early I know- but there were none listed for Tuam at that time,which may be significant. And only one O'Donnell- so it is a possibility. Any marriage would normally take place in the female's home parish. If Patrick was away from home,or his wife was also a teacher,then they could have married anywhere. Have you had a look at the 1901 census for Tuam? Or the 1911 might be more useful,as it gives the number of years married,so you could work out the exact year of marriage with some degree of accuracy (he was a teacher after all!) I searched for an Isaac O'Donnell/Isaac Shiel anywhere in Ireland,assuming your grandfather was named after his,or some other near relative. There was an Isaac Shiel married to Winifred Kerrans in Foxford,Mayo having kids in the 1860s and 1870s.Mary could fit this time frame,and Foxford is only 30 miles from Tuam. On the whole,Isaac is a rare name in Galway.It's found most frequently in the northern counties. I assume you checked for all variations of O'Donnell as well as Shiel? Have you looked at the Tuam parish registers? Were there any siblings? Cathy