Unexpected DNA Results: When a Parent Isn't Who You Thought

DNA tests regularly reveal unknown siblings, adoptions and different biological parents. How to confirm what the results mean, take care of yourself, and decide what to do next.

3 min read

DNA tests don't keep family secrets. Every day, testers discover that a parent isn't their biological parent, that they have half siblings they never knew about, or that a grandparent was adopted. The community often calls these discoveries NPEs, originally "non-paternity events," now usually "not parent expected." They're far more common than most people realize, and they can be deeply unsettling. If this has happened to you, you're not alone.

First, take a breath

An unexpected result can feel like the ground has shifted under you. It's normal to feel shock, grief, anger, confusion or even relief. Take time before acting or telling anyone. There are support communities specifically for people in this situation, including groups for those who discovered a different biological father, adoptees, and donor-conceived people. Talking with others who've been through it can help a great deal, as can a counselor familiar with DNA discoveries.

Confirm what the results mean

Before drawing conclusions, make sure you understand the evidence:

• Check the cM amounts. How much DNA do you share with the match that surprised you? Compare it to the expected ranges for different relationships. See Shared cM Explained.
• Check known relatives. Are you matching your father's known relatives, such as his siblings' children? If you share far less DNA with them than expected, or none, that's significant. A first cousin should share around 866 cM; a half first cousin around half that.
• Look at shared matches. Do your matches sort into the family lines you expected? See Sorting Your DNA Matches.
• Consider other explanations. Could a sibling actually be a half sibling? Could a match be related to you in more than one way? Could the other person's tree be wrong, rather than yours?

An experienced genetic genealogist, or volunteers in DNA help communities, can help you interpret the numbers if you're unsure.

Common explanations

• A different biological father, through an affair, an earlier relationship, or an assault
• Adoption, formal or informal, sometimes within the family (a grandmother raising her daughter's child as her own)
• Donor conception, through sperm or egg donation, sometimes undisclosed
• A mix-up such as a hospital switch, which is rare but has been documented
• A discovery about an earlier generation, such as a grandparent or great-grandparent who wasn't the biological child of their parents

Identifying a biological parent

If you want to identify an unknown biological parent, the methods are the same ones adoptees use:

1. Start with your closest unknown matches, such as half siblings, aunts, uncles and first cousins.
2. Build their family trees using records, back to their grandparents.
3. Look for where the trees of several matches meet; your unknown parent is likely a descendant of that couple.
4. Use ages, places and the cM amounts to narrow down which person in that family fits.

See Finding Birth Family for more detail. Volunteer "search angels" in DNA help groups assist with this every day.

Deciding what to do

There's no single right path. Questions to think about:

• Do you want to ask your mother or other family members? They may have answers, or may not know. Consider how and when to raise it, and how they might react.
• Do you want to contact biological relatives? Some welcome contact; others are shocked or unwilling. A gentle first approach, with time to respond, usually goes best. See Writing to DNA Matches.
• What about medical history? Knowing your biological family's health history can matter to your own care.
• What about your identity? Many people find that their sense of family includes both the family that raised them and their biological family. You get to decide what this means to you.

Respect everyone's privacy

A discovery about you is also a discovery about others: a parent's past, a stranger's family. Be thoughtful about what you share publicly, including in online forums and family trees. Use privacy settings, and avoid naming living people in public posts.

For genealogy: record what's true

When you're ready, record your biological relationships in your research tree, with the DNA evidence as a source. Many programs let you mark a relationship as biological, adoptive or step. You can include both the family who raised you and your biological family. Family history is big enough for both.