Hi there!
First... some background
I've been trying to substantiate whether Andrew Forbes, who lived in Johnstone, Renfrewshire (m. 1792) is the father of my 4x Great Grandfather, William Forbes (b. 1806-11) who was a blacksmith in Girvan, Ayrshire.
I have some reasons to suspect this patrilineage (despite the substantial distance between Girvan & Johnstone):
- William Forbes' sister, Helen, was born in Johnstone, Renfrewshire.
- William's first born son was named Andrew. (Consistent with Scottish Naming Patterns).
- Andrew Forbes had a son named William, born 1806, according to a birth record. Right timeline.
- Most of Andrew Forbes' children worked as blacksmiths. As did most of William Forbes' children.
Testing the theory with DNA
What I had hoped to accomplish was to provide another layer of substantiation to this theory before I moved on in my research.
The documentation all points positively, but would DNA substantiate or contradict the theory?
So I built a large family tree and tracked down three known distant descendants of Andrew Forbes who had all taken DNA tests: two six cousins, and a fourth cousin (2 times removed). Two of the descendants weren't interested. One of the sixth cousins had agreed to export her Ancestry.com file and I did a Autosomal One-to-one Comparison on GEDmatch.
These were the GEDmatch comparison results:
Largest segment = 4.4 cM
Total Half-Match segments (HIR) 18.3cM (0.511 Pct)
5 shared segments found for this comparison.
417967 SNPs used for this comparison.
52.479 Pct SNPs are full identical
My question for the forum is whether this provides credence to the theory that William is Andrew's son? It looks to me like the result is consistent with a sixth cousin and therefore doesn't contradict anything (?), but how different in terms of cM would a random person (a control) be from a sixth cousin? Is there a next step I should take?