DNA tests are triggering a wave of ‘surprise heirs’ asking for a slice of inheritances. Lawyers urge estate planners to add these 2 protections

In Massachusetts, for example, Carmen Thomas discovered the identity of her biological father and two half-sisters after using a consumer DNA test. The next year, she filed a suit against them seeking a portion of a $28-million medical malpractice award tied to their late father, according to a story in the Wall Street Journal.

So, while families might think their estate planning is airtight, intestacy rules or ambiguous language could create openings for a will challenge. Inheritance laws also vary by state, adding to the complexity (2).

The legal consequences of unknown heirs

One in five Americans (21%) has taken a DNA test, according to a YouGov survey, with those 65 and older (28%) slightly more likely than younger adults to have done so (3).

“Surprise heirs like Thomas are popping up because of DNA test kits,” according to the Wall Street Journal article. While states are “grappling with how to rewrite laws to address the issue,” lawyers are “encouraging people to rethink their estate plans.”

Not only can this process be emotionally draining for all parties involved, it can delay the distribution of assets, create conflict where assets have already been distributed and drain tens of thousands of dollars in legal costs (1).

That’s why some heirs may choose to settle, even if the claim is thin, because litigation can be expensive and time-consuming.

Even worse is if someone dies without a will or trust. That means their estate would fall under state-specific intestacy rules, which determine how their assets will be divided (4).

Only about one in four Americans (24%) have a will in 2025, compared to 33% in 2022, according to Caring’s 2025 Wills and Estate Planning Study (5). And Americans with children under the age of 18 comprise “the largest cohort of people without wills or other estate planning documents” (5).

Intestacy rules generally prioritize a surviving spouse, biological and adopted children, grandchildren, surviving parents and siblings — and then move down the family tree. But in many states, common-law partners may be excluded (4).

So, if a newly discovered biological child comes out of the woodwork and proves paternity, then that child may be in the line of succession, perhaps even ahead of other family members or a common-law partner.

How to make sure you choose who inherits

There are two protections that can help protect families from unanticipated DNA-based claims: a will or a trust.

If you don’t have a will, there’s no time like the present to create one. If you do have one but haven’t updated it in a while, you may want to do that as soon as possible (especially if you’ve since married, had a child or gotten a divorce).

The will should clearly name all heirs (and not use vague language like “descendants”). If you want to intentionally exclude certain people (including unknown biological children), you could include a disinheritance clause in your will.

A disinheritance clause is a provision that “addresses your intent to not provide for any known or unknown children or children adopted or born after the execution of the documents,” according to Jennifer Rouse, a certified specialist in estate planning, trust and probate law with Meissner Ruggles Thompson in California.

While it sounds harsh, it could help you have control over who you want to inherit, whether they are related by blood or not.

Another consideration is whether the grantor of the will had previously donated sperm or an ovum — and this can also be included in the disinheritance clause.

In California, for example, code sections outline that “a donor who is not a spouse of the parent is not considered a parent for any reason,” writes Rouse. “But not all states have similar provisions, or the donor may not be alive to explain the circumstances to make it clear that they were a donor” (6).