In Common With Tools: Use Your Tools

It is loudly and regularly suggested you test anyone and everyone you can, and with good reason!  Earlier in the year, Blain Bettinger invited the genetic genealogy community to furnish him with, “information about the amount of DNA shared by people having a known genealogical relationship. “  You can read the results of Blain’s study here.

Blaine collected data out to known third cousins.  As I would like to see more of my (and the preceding generations) 1^st and 2^nd cousins test, and I have four generations of immediate family tested through FTDNA’s Family Finder, I decided to run an experiment of my own. It was my hope that the results would intrigue untested relatives to consider participating in the study.

Had I not harassed persuaded my close relatives to test, I would have a great deal less data to work with, fewer lines proven, and a much harder time discovering relatedness to matches.  Having my grandmothers’ data has also unlocked an ancestral picture that had largely evaporated by the generation of my children.

If you are a member of FTDNA, you can use the In Common With tool to see matches you have in common with another tester.  For close relatives such as parents/children, this will help determine whether the match in common is maternal or paternal.

Leona:

310 Total matches

• Jackie: 130 matches in common.  3381.16 cM shared (parent/child)
• Lori: 100 matches in common.  1918.26 cM shared (grandparent/grandchild)
• Jeremy: 30 matches in common.   820.74 cM shared (great-grandparent/great-grandchild)
• Gavan: 60 matches in common.   932.45 cM shared (great-grandparent/great-grandchild)

As you can see, Leona’s great-grandsons share 60 and 30 matches with her.  Had they been the first generation to test, and had only Gavan tested, he would have lost half of his generation’s potential connections.

Gladys:

660 Total matches

• Stephen: 260 matches in common.  3382.68 cM shared (parent/child)
• Lori 180 matches in common.  2011.93 cM shared (grandparent/grandchild)
• Jeremy  50 matches in common.  965.18 cM shared (great-grandparent/great-grandchild)
• Gavan 110 matches in common.  1110.03 cM shared (great-grandparent/great-grandchild)

Similarly, Gladys’s great-grandsons share a markedly different number of matches with their great-grandmother.   Had Jeremy and Gavan been the only members of the family to test, not only would they have lost between 610-540 of her matches, but also would also have needlessly lost 60 of them if only Jeremy had tested

Stephen:

370 Total matches

• Gladys: 260 matches in common.  3382.68 cM shared (parent/child)
• Lori: 170 matches in common.  3382.91 cM shared (parent/child)
• Jeremy: 50 matches in common.  1612.12 cM shared (grandparent/grandchild)
• Gavan: 110 matches in common.  1910.94 cM shared (grandparent/grandchild)

Fortunately, my grandmothers were able to test.  Otherwise, had my father been the oldest generation to test, we would have lost 400 of my paternal grandmother’s matches.  Had I been the oldest generation to test, we would have lost nearly 500 of my grandmother’s matches and 200 of my dad’s.

On the maternal side of the family, I have a full aunt and a half aunt who have tested.  They share the same father who is unavailable to test.

Jackie:

500 total matches

• Leona: 130 matches in common.   3381.16 cM shared (parent/child)
• Diane: 130 matches in common.  1770.68 cM shared (half siblings)
• Lori:  160 matches in common.  1882.17 cM shared (aunt/niece)
• Jeremy: 50 matches in common.  989.45 cM shared (great aunt/great nephew)
• Gavan: 60 matches in common.  788.90 cM shared (great aunt/great nephew)

Diane:

530 Total Matches

• Jackie: 130 matches in common.  1770.68 cM shared (half siblings)
• Lori: 50  matches in common.  683.35 cM shared (half-aunt/half-niece)
• Jeremy: 40 matches in common.  411.12 cM shared (half great aunt/half great nephew)
• Gavan 30 matches in common.  290.97 cM shared (half great aunt/half great nephew)

Jackie inherited 180 of her mother Leona’s matches, and the other 320 matches, excluding IBS can be assigned to the father she and Diane had in common.  However, of those 320 matches, Jackie and Diane only have 130 in common.  Had both sisters not tested, we would have lost a potential 190 matches from my paternal grandfather.  I have also tested, and have 50 matches in common with Diane, which could only have come from their shared father and my paternal grandfather.  Had Diane and I been the only members of the family to test, we would only be able to confirm those 50 matches as derived from my paternal grandpa.

Had testing begun with my generation in tandem with my sons we can see from the figures below how many matches would be lost and unassigned:

Lori:

540 Total matches

• Leona:  100 matches in common of 310. 1918.26 cM shared (grandparent/grandchild)
• Gladys: 180 matches in common of 660. 2011.93 cM shared (grandparent/grandchild)
• Stephen: 170 matches in common of 370.   3382.91 cM shared (parent/child)
• Jackie: 160 matches in common of 500. 1882.17 cM shared (aunt/niece)
• Diane: 50 matches in common.  683.35 cM shared (half-aunt/half-niece)
• Jeremy: 130 matches in common.  3378.94 cM shared (parent/child)
• Gavan:  210 matches in common.  3382.74 cM shared (parent/child)

Jeremy:

570 Total matches

• Lori: 130 matches in common.  3378.94 cM shared (parent/child)
• Stephen: 50 matches in common.  1612.12 cM shared (grandparent/grandchild)
• Gavan: 80 matches in common.  1464.48 cM shared (half siblings)
• Gladys: 50 matches in common.  965.18 cM shared (great-grandparent/great-grandchild)
• Leona: 30 matches in common.  820.74 cM shared (great-grandparent/great-grandchild)
• Jackie: 50 matches in common.  989.45 cM shared (great aunt/great nephew)
• Diane: 40 matches in common.  411.12 cM shared (half great aunt/half great nephew)

Gavan:

700 Total Matches

• Lori: 210 matches in common.  3382.74 cM shared (parent/child)
• Stephen: 110 matches in common.  1910.94 cM shared (grandparent/grandchild)
• Jeremy:  80 matches in common.  1464.48 cM shared (half siblings)
• Gladys: 110 matches in common.  1110.03 cM shared  (great-grandparent/great-grandchild)
• Leona: 60 matches in common.  932.45 cM shared  (great-grandparent/great-grandchild)
• Jackie: 60 matches in common.  788.90 cM shared (great aunt/great nephew)
• Diane: 30 matches in common.  290.97 cM shared (half great aunt/half great nephew)

My sons would have lost between 280-250 of the matches we gained by testing my maternal grandmother.  They would have lost between 610-550 of the matches we gained by testing my paternal grandmother.  Had Jackie not tested, they would have lost her 320 matched attributed to my maternal grandfather.  Had Diane not tested, they would have lost between 90 and 100 matches with my paternal grandfather.

If you are wondering whether it is worth having those aunts/uncles/siblings/sibling of your grandparents/cousins etc tested, it is!  In my case, we have found it invaluable.

More about Gladys and Leona’s statistics and ancestral backgrounds can be learned here.