Prenups and Inheritance: How Couples Plan for Family Wealth

Why Inheritance Is Not Always Kept Separate Automatically

The assumption trips up more couples than almost any other: "My inheritance is mine, so I don't need to write anything down." In most states, inheritance is treated as separate property, meaning it belongs to the person who received it rather than to both partners. That default holds when a gift or inheritance stays clearly in one person's name and never blends with shared money.

The problem starts with commingling. Commingling is the moment separate property mixes with marital property so thoroughly that a court can no longer tell where one ends and the other begins. Once that happens, inheritance can become partly or fully subject to division if the partnership ends. Inheritance can lose its separate status in ways that feel completely ordinary at the time.

Common commingling scenarios include:

• Depositing inherited money into a joint bank account you both use.
• Using inheritance to buy a home or other property titled in both names.
• Mixing inherited funds with marital savings until the paper trail disappears.
• One partner contributing significant time, money, or labor to maintaining or improving an inherited asset (a family lake house, for example, or a rental property).

None of these actions require bad intent. They happen because life is shared and money moves. That's exactly why writing down your intentions in advance creates real clarity. As Michael C. Cotugno, Esq., Managing Partner, Neptune Legal, puts it: "A premarital agreement doesn't have to be a wedge between partners or a necessary evil that protects assets at the expense of trust and intimacy." A prenup lets you both agree, calmly and in writing, on how inherited wealth should be treated, long before anyone has to guess.

How a Prenup Addresses Inheritance and Future Inheritance

A prenup is a written contract you sign before marriage that outlines how you'll treat assets and financial responsibilities during the partnership and if it ends by divorce or death. When it comes to inheritance, it lets you both define terms that state law would otherwise decide for you.

A well-drafted agreement can define:

• Which property is separate. This includes what each partner brought into the marriage plus any gifts or inheritances received during it.
• How future inheritances will be treated. You can address wealth you haven't received yet. If you're a named beneficiary of a family estate, assets you have not yet inherited can still be addressed in advance so you and your partner share the same expectations.
• Whether appreciation stays separate. If an inherited investment portfolio or piece of real estate grows in value during the marriage, the agreement can spell out who that growth belongs to.
• How shared purchases funded by inheritance are handled. If inherited money helps buy a jointly used home, you can agree upfront on how that contribution is treated.

Here's the part many couples miss: a valid prenup can override default state property rules and even a surviving spouse's right to inherit. This works in both common law states (which give a surviving spouse the right to claim a portion of the estate) and community property states (which treat most earnings during marriage as jointly owned). In effect, you and your partner get to contract for the outcome you both want, rather than leaving it to a judge and a statute.

Family Businesses, Trusts, and Multigenerational Assets

Family wealth rarely sits in a single bank account. It shows up as a business, a portfolio, real estate, or assets held in trust, and each type raises its own questions.

A prenup can identify family business interests and trust distributions as separate property and clarify how business appreciation is treated during the marriage. This matters because a business often grows precisely during the years a couple is together. Without a written agreement, a partner might later claim a share of that growth even if the business was inherited or owned before the marriage. Defining the treatment of appreciation in a family business up front removes that ambiguity.

Prenups also work alongside other planning tools rather than replacing them. Irrevocable trusts (arrangements you generally can't change once created) and limited liability companies (LLCs) can add layers of clarity around ownership. Trusts and LLCs used together with a premarital agreement give families more than one way to keep multigenerational assets organized. One reason coordination matters: divorce courts have increasingly considered inheritances and trust distributions when valuing and dividing marital property, so relying on a trust alone may leave gaps a prenup can address.

Michael C. Cotugno, Esq., Managing Partner, Neptune Legal, frames the bigger picture this way: "For conscious partners, wealth is not merely a collection of assets; it's a powerful tool with the potential for profound purpose." Planning for how family wealth passes across generations is part of using it well.

Common Law vs. Community Property States and Default Rules

Where you live decides your default rules, and those defaults vary a lot. Absent a prenup, the laws of the state where you're domiciled at the time of divorce or death control what happens to your income, assets, and liabilities. States differ on how they define marital versus non-marital property, how they value and distribute it, how they treat appreciation of separate property, and what rights a surviving spouse has to a deceased partner's estate.

Here's how the two systems compare against a written agreement:

That last row is the one people underestimate. ZIP codes change over a lifetime. You might sign a prenup in one state and retire in another with very different rules. A written agreement creates portable consistency, so the terms you and your partner agreed to don't quietly shift the day you cross a state line. Because these rules are technical and state-specific, this is genuinely an area where working with an experienced attorney pays off.

How Neptune Guides Couples Through Inheritance Planning

Most couples don't want to become experts in equitable distribution law. They want a clear plan and a calm process. That's what Neptune manages end to end.

Neptune pairs you with experienced attorneys, Certified Financial Planners (CFPs), and CPAs, each with 20+ years of experience, and shepherds the full process from the first conversation to signed documents. This isn't a DIY template and it isn't a marketplace where you're handed a list of names and left to sort it out. AI-guided education and conversations help you understand each decision along the way, while the professionals handle the substance.

We treat a prenup as one integrated piece of a broader estate and financial plan, coordinated across disciplines so your agreement, your will, your trusts, and your tax strategy all point in the same direction. A prenup and your estate plan work together rather than in isolation.

A few requirements hold no matter your situation. For a prenup to be upheld, it generally must be in writing and signed voluntarily by both partners, with honest financial disclosure from each. Independent counsel for each partner is highly recommended for an enforceable prenup. And like your estate plan, you should revisit the agreement every few years so it keeps reflecting your circumstances as they change. Couples who plan together, grow together, and this is what planning together looks like in practice.