How much of your Parents’ DNA do you and your siblings have altogether?

You share some DNA with your siblings, which means if you have enough siblings you have all of your parents' DNA, but how much DNA?

In the Genetic Genealogy Tips and Techniques Facebook Group, there was a discussion a couple of weeks ago about, “How much DNA do siblings, as a group, share with their parents?”

We know that a single child shares 50% of each one of their parents’ DNA. Now, theoretically, if you add another child, so you have two siblings, then those two siblings should share around 75% of both of their parents' DNA. Adding a third sibling, you’re gonna go up to 88%.

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What you can see from this pattern is that half of the amount left is added on for each sibling. Each sibling adds less and less of the total DNA that your parents have. At some point, you’re going to get to the point where you basically have all of your parents' DNA.

However, DNA doesn’t theoretically combine and recombine exactly how statistics show us. What we can use is some of the information that people already have gathered to see what this range is.

Theoretically, with two siblings the percentage shared should be around 75%, but we want to know the range of shared DNA.

DNA painter can demonstrate the range. If grandparents and their grandchildren have taken DNA tests, then when you look at where they match DNA, you’re actually looking at the parents and where the recombinations happened. By comparing a set of siblings to a grandparent, you can figure out how much of the parent’s DNA that set of siblings has.

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Andy walks through the steps of how to accomplish this task using DNA painter.

What You’ll Need:

  1. You’ll need a free DNA painter account, which will have some limited tools that you can use. If you already have a DNA painter account, you’re going to need to use a profile. If you’re not a subscriber, you need to delete your current profile to do this, or you can subscribe and be able to have as many profiles as you want.

  2. You’ll need to use your DNA kit information from a testing company for this process to work. Andy shares an example from 23andMe and GEDmatch.


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