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Why Your Siblings’ Results Might Surprise You

It is often thought and is a misconception that if siblings have the same parents, their DNA should be the same. Understanding the potential difference in ancestry DNA tests is essential to understand how DNA tests work.

DNA tests provide individuals with 50% of the father’s and 50% of the mother’s genes. So why does it vary between siblings and their ability to show differences in their ancestry?

Genetic recombination is a process that a fetus goes through and divides chromosomes and genetic information. This process creates a unique genetic makeup for each person, although they still have 50% of the father’s and 50% of the mother’s genes. If two siblings have parents with British and African ancestry, one may show more genes in the British ancestry and the other may show more in the African ancestry. It does not mean they have changed 50% of mothers’ and 50% of fathers’ genes. It is a fascinating process in human genealogy.

That is why two siblings could look different from each other, one with blue eyes and blond hair and the other with brown eyes and dark hair. They are still biological siblings with the same parents.

Understanding Different Ancestry Results in Siblings

Ancestry results may differ in siblings as everyone’s DNA is processed through a combination of sections of DNA by a person. Due to the division of chromosomes in each person, they create unique combinations of genes. These are the genes that are analyzed in the DNA process. The most dominant gene in a person is the one that will be reflected in each person, and these can differ between 2 individuals as they each have different genetic makeup.

Unless siblings are identical twins’ ancestry, DNA testing will show variation in your genetic DNA.

Why Siblings Can Have Different DNA Heritages

Siblings can have different ancestry indicators impacting their genes because the chromosome splitting between them varies, creating different genetic markers. The higher the mix of origins, the higher the gene pool (Ancestral Informational Markers) that is inherited.

This does not mean the markers do not show that they are related. They show their relationship, but each person will have different dominant markers. Both are correct results.


Ancestry DNA testing is a thrilling experience. It gives individuals insights that they might never have known. It creates connections in social, International, and family circles. It explains why siblings can look very different although they come from the same parents.