View Full Version : How to prove a relationship theory?

29-04-2018, 3:04 PM

I am trying to discover my mother's paternal family. From my grandfather's birth certificate we have his mother's name only - Kate Taylor - no age.
The baptism certificate is the same but gives the address of my grandfather's guardian's parents.
I have a theory that his guardian's illegitimate son was actually my grandfather's father and he certainly grew up with the family until his marriage at 22.
I have now identified a potential (half?) 3rd cousin of my mother's based on this relationship but there is no match shown via their respective DNA tests - should I read anything into this?
I have also found a potential 1st cousin 1 x removed based on a best guess of the "right" Kate Taylor - how likely is it that a DNA test would prove/disprove this relationship or is the fact that my grandfather would only be a half-brother and therefore it is a half-1st cousin once removed make it too remote?

Lesley Robertson
29-04-2018, 4:27 PM
To prove a possible relationship of males, you need an unbroken male line of descent because you need matching Y chromosomes. Of course that wouldn’t tell you whether it was the son, a brother, the father or even an uncle... or anyone else’s with an unbroken male line back.

What a DNA match proves depends on which type of analysis has been done, but if there’s no match then there’s no relationship within the limits of the analysis. The most extreme example to clarify this would be no match when you check the Y chromosome (no male relationship), and a match when you check the mitochondrial DNA which descends. Is the female line and would indicate a relationship along the female line. Between the two extremes, and more complexities.