06 September 2019

Help Your DNA Match Expand their Family Tree

Show your DNA match who's the genealogist in the family!

You've probably got more genealogy skills than many of your DNA matches. If you want to figure out your connection, why not do some of the work for them? We all complain about our matches' missing or flimsy trees. Let's put some more leaves on their trees.

It helps if you can spot the best place to dive in.

My dad and I have one DNA match, Annie, who shares 44 cMs (centiMorgans) with him and (surprisingly) 43 cMs with me. Annie has a very small family tree posted. It doesn't have a lot of facts. But 5 of the 13 people in the tree have my 2nd great grandmother's last name.

That's our only apparent connection: the last name Girardi. Now, I know that name comes from more than one part of Italy. Former Yankees manager Joe Girardi's ancestors came from up north. My people are all from southern Italy.

But that name is the place for me to dive in.

If you're a genealogy warrior, why not help your DNA match find their missing link to you?
If you're a genealogy warrior, why not help your DNA match find their missing link to you?

I decided to see if Annie's Girardi ancestor was born in my 2nd great grandmother's town. Annie's tree had no date for Luciano Girardi's birth. But it had a December 1900 date for Luciano's wife. I went to my folder of 1900 birth records from the town of Pescolamazza.

There she was: Lorenza Immacolata Viglione. And in the margin of her birth record was the date of her marriage to Luciano Girardi.

Now I was sure this Girardi family was from my Girardi family's hometown. And it's a small town, not a city.

I went year by year, checking each birth index for Luciano Girardi. I found him in 1892 and held my breath. Was he a fit for my family tree?

Both his father and his mother were named Girardi. Even though neither of his parents were in my tree, I had my marching orders. Because of his birth year, one of Luciano's parents might be my 2nd great grandmother's 1st cousin.

Let's play a little game, shall we?

Annie seems to be the child of Luciano. That'd put her close to my father's age, just for reference.

Imagine Luciano's parent is my 2nd great grandmother's 1st cousin. If so, Annie's 3rd great grandparents are my father's 4th great grandparents. She would be my father's 3rd cousin once removed. (I had to draw it to make sense of it.)

I couldn't do this in my head if I tried. A drawing helped me understand the theoretical relationship.
I couldn't do this in my head if I tried. A drawing helped me understand the theoretical relationship.

Ancestry DNA estimates Dad and Annie are 4th–6th cousins. I checked the "consanguinity relationship chart" from Family Tree UK that I mentioned last week. With their shared 44 cMs of DNA, Annie and my dad could most likely be:
  • 1st cousins 4 times removed
  • 2nd cousins twice removed
  • 2nd cousins 3 times removed
  • 3rd cousins
Each of the above relationships has the exact same probability based on the numbers.

Now let's add in the "divide by 68" rule from last week. Dividing their shared 44 cMs by 68 tells me that Dad and Annie share .647%, and Annie and I share .632% of our DNA. Wow. We share such a small percentage of DNA with our not-so-distant-cousins. Even 2nd cousins share only about 3.125% of their DNA.

I sent Annie a link to Luciano and Lorenza's Italian birth records. But I need to keep researching. I need to investigate these new Girardi names. I need to find Italian documents for them and hope to connect them to my family.

Knowing your possible relationship to a DNA match won't solve the puzzle. As you do the genealogy research, keep those possible relationships in mind. Draw yourself a diagram. You can solve many of your DNA relationships this way.


  1. I can't stress enough how important this exercise is. I've just cracked the connection I wrote about in this article, and my relationship to Annie is exactly what I hypothesized it would be!!!

  2. It is so much fun when you find the connection. I do a drawing as you did and I use the relationship tool in Family Tree Maker Software to help me figure out the relationships. I also use a relationship calculator I found that can be very helpful: http://www.searchforancestors.com/utility/cousincalculator.html but I find if I draw it out it makes it much clearer to me. When I do find the connection I write to the DNA match and send them the documents I have found to show the connection. But believe it or not some don't respond!