Siblings Can Have Surprisingly Different DNA Ancestry

When it comes to tracing your roots through your genes, biological siblings may have less in common than many people expect. The fact is that one sibling might inherit more from Mom than from Dad while the other sibling might inherit a different mix.

An article by Nicole Wetsman in the National Geographic web site explains it all at


No, the article doesn’t quite say that. You always inherit 50% of your DNA from each parent, but your sibling may inherit a different subset of 50% from each parent. Theoretically, you could have absolutely no DNA in common (if you each inherited the opposite 50% from each parent), but in reality that’s pretty much impossible. Statistically, on average, siblings share 50%; the range is more like 30-55%. Unless they are identical twins, of course.
Recombination, which creates the random mix from each parent, occurs before fertilization.


Jul is correct.
Each parent contributes 50% but the portion of their parent’s DNA that is passed on to the grandchild can be different. For example, my son inherited about 25% from each of my parents but about 30% from one of my wife’s parents and 20% from the other.


Let me tell you thisj story, a parent sent in a sample for each of 3 chiildren. All had the same parents. Two of the children matched but the 3rd didn’t match either.


    If a child doesn’t match either parent, then either their test tube was mishandled or the child was mishandled just after birth in the hospital.


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