A DNA Breakthough

For over 50 years I have been looking for the parents of my great great grandfather Andrew Buchanan, who brought his family to Canada from County Tyrone, Ireland in 1847. We may have found them, thanks to an autosomal "Family Finder" DNA test done by my cousin Darlene. One of the matches is an S. D. Keys, shown as a 2nd to 4th cousin.

This is someone we have been in touch with over recent years and if his 2GGF Samuel Buchanan was a brother to our Andrew Buchanan, then he would be a 4th cousin to Darlene. But it gets better. Samuel's wife Matilda was also a Buchanan by birth, which means that he received a double-dose of Buchanan DNA, so he might appear as a 2nd cousin.

.Various sources indicate that Matilda was born in Castlederg and Samuel in Cooel/Coolavanagh.
Matilda appears as the daughter of Joseph Buchanan and Nancy Carson, and Samuel as the son of John Buchanan and Mary (Molly) Caldwell.

Genetically, Andrew could be the son of either of these sets of parents, depending whether he was a brother to Samuel or Matilda. But since the names Matilda, Joseph, and Nancy (Ann) are rare in Andrew's family, it seems probable that Matilda was the sister-in-law and not the sister. The names Samuel and John are very common in Andrew's family.

We have close YDNA matches with the Buchanans of Cooel and of Kirlish. S. D. Keys would not appear as a YDNA match because this test follows the male ancestral line. His male line would be Keys rather than Buchanan.

So it appears highly probable that John Buchanan and Mary Caldwell of Cooel are Andrew Buchanan's parents. 

Good work Darlene!