23andMe and Surprise Heirs

Estate planning in the age of home DNA tests

Not long ago, a person’s family tree was built from birth certificates, old photos, and family stories. Today, it can be built for $99 and a bit of saliva. 

Consumer DNA testing services like 23andMe and AncestryDNA have become mainstream. Millions of people have used them to learn about their ancestry — and, increasingly, to discover previously unknown relatives: half-siblings, biological parents, and children no one knew existed. Personally, I’ve used 23andMe and the reports are super interesting.

That has led to a new and very real estate-planning question: What happens if someone discovers they are related to you after your death — and then claims an inheritance?

The “surprise heir” problem

This is no longer a hypothetical. There have been several cases where someone:

• Took a home DNA test

• Discovered a biological relationship to a deceased person

• Then attempted to assert legal rights as an heir

Sometimes those claims fail. Sometimes they succeed. But almost always, they create conflict, delay, and expense for the people left behind.

The risk is highest when someone dies without a clear estate plan — or with documents that don’t anticipate modern DNA discovery.

What happens without an estate plan?

If there is no valid will or trust, state intestacy laws control. Those laws prioritize heirs by blood and legal relationship — not by who the person intended to benefit.

Here’s how that can play out in the states where many of my clients live:

Oregon

Oregon allows inheritance by children born outside of marriage if parentage can be established. DNA evidence can be part of that proof. If someone dies intestate, a newly discovered child may have a viable claim.

Washington

Washington has adopted a modern parentage statute that expressly recognizes genetic testing. Washington is procedurally friendly to DNA-based parentage claims — though a claimant still must qualify as a legal heir.

California

California is more restrictive, but not immune. DNA alone is not enough, but a claimant may inherit if parentage is proven and there is evidence the decedent “held the child out” as their own. California also has strong pretermitted heir protections that can surprise families when a will is outdated.

The common thread: without an estate plan, the law, rather than your intent, decides.

The good news: this is very fixable

A properly designed will or revocable living trust can largely defeat “surprise heir” claims, even in the age of home DNA testing.

The key is clarity.

Well-drafted documents should:

1. Clearly define who counts as a “child”

Modern estate plans often define children as those:

• Born to or legally adopted by the client, and

• Whose parent-child relationship was established during the client’s lifetime

This prevents post-death DNA discoveries from expanding the class of beneficiaries.

2. Expressly exclude unknown or later-discovered relatives

Good planning documents now routinely state that:

• Anyone not expressly named is intentionally excluded

• Biological or genetic relationship alone is not enough

Courts generally respect this kind of clear intent.

3. Avoid intestacy entirely

A fully funded trust avoids probate and eliminates gaps where state law might otherwise step in.

4. Address pretermitted heir statutes

Especially in California, estate plans should include language making clear whether later-discovered children are intentionally omitted.

Why this matters now

Twenty years ago, most people reasonably assumed that unknown heirs would remain unknown.

That assumption no longer holds.

DNA testing has changed the information landscape, not the law — but that information can trigger legal claims, emotional disputes, and costly litigation if an estate plan isn’t designed for modern realities.

The bottom line

Home DNA testing has made it easier to discover biological relationships — but it hasn’t replaced the importance of clear estate planning.

With a thoughtfully drafted will or trust, you can:

• Control who inherits

• Reduce the risk of surprise claims

• Protect the people you actually intend to benefit

And most importantly, you can spare your family from fighting battles you never intended them to fight.