Ancestry DNA can trace your genetic heritage and family tree back hundreds to thousands of years, depending on what you’re looking at:

1. DNA Ethnicity Estimates

• Time Depth: Up to 1,000+ years ago

• What it shows: Where your ancestors likely lived and how your DNA matches current populations.

• Limitations: It’s an estimate based on modern reference populations, so it gives broad regional insights, not exact ancestors.

Maternal and Paternal Lineages (if available)

• Time Depth: Up to tens of thousands of years ago

• What it shows: Your haplogroups, which are ancient DNA signatures passed down from your mother (mtDNA) and father (Y-DNA for males).

• Use: Helps trace ancient migration patterns, like if your paternal line came from the Middle East or Northern Europe.

Family Tree & Records via Ancestry.com

• Time Depth: Typically 150–300 years (5–10 generations)

• What it includes: Census records, birth/death/marriage records, immigration documents, and more.

• Limitations: Depends on how much data you or others have added and where your ancestors lived (some countries have better records than others).

Summary:

Yes, two siblings can have different AncestryDNA results—and that’s completely normal.

Why it happens:

Siblings each inherit 50% of their DNA from each parent, but not necessarily the same 50%. The specific combination of genes passed down is random.

What this means:

• One sibling might inherit more DNA from, say, a grandparent of Italian descent, while the other gets more from a grandparent of Irish descent.

• As a result, their ethnicity estimates can differ, sometimes significantly, even though they share the same parents.

But some things stay consistent:

• Siblings will share a high amount of DNA, typically around 50%.

• They will appear as close matches (siblings) in the DNA match section of AncestryDNA.

Example:
One sibling might be 30% Scandinavian and 20% West African, while another is 25% Scandinavian and 25% West African.

Ancestry DNA tests are generally quite accurate for what they are designed to do, but their accuracy varies depending on the specific feature:

1. Ethnicity Estimates

• Accuracy: Approximately 70–95%, depending on the region.

• Details: The test compares your DNA to reference samples from various populations. It’s more accurate in well-represented regions (like Europe) and less precise in underrepresented areas (like parts of Africa or Asia).

2. DNA Matches (Genetic Relatives)

• Accuracy: Very high for close relatives.

• Details: First to third cousins are usually detected with over 99% accuracy. The farther the relation, the less precise the estimate becomes.

3. Maternal & Paternal Lineage (mtDNA and Y-DNA)

• Accuracy: High for deep ancestry tracing.

• Details: These tests trace unbroken maternal or paternal lines and are based on specific DNA segments (mtDNA and Y-DNA). They’re excellent for understanding ancient origins and haplogroups, but not useful for detecting recent relatives.

Important Considerations:

• Not a diagnostic tool: It doesn’t test for health conditions unless specified.

• Reference panels vary: Different companies have different databases, which can affect your ethnicity results.

• Updates: Results may change slightly over time as databases grow and algorithms improve.