Honouring a Mutual Will Promise Before a Second Marriage

The situation

Selam, a retired air traffic controller in Cambridge, came to our team a few months before her planned wedding to Natalia, a university professor. It was a happy reason to need a lawyer, but Selam arrived with a specific worry rather than a general one. Twenty-two years earlier, she and her first husband, Hodan, had made what are commonly called mirror wills, drafted at the same time, on the same terms: each left everything to the other on first death, and on the death of the survivor, the entire estate would go to their two children, split equally. When her husband died, Selam inherited under that plan and never seriously revisited it. Her estate now, mostly the family home and a mix of pension and investment accounts, was worth roughly $1.8 million.

What made her wills unusual, though she had not fully appreciated it at the time, was a conversation she and her husband had with a lawyer decades ago about making the arrangement binding rather than a simple mirror. They had signed a written agreement, referenced in both wills, that neither would change the terms after the first death. That agreement is what turns ordinary mirror wills into what the law calls mutual wills, and it is a much stronger commitment than most people realize when they sign one.

The legal problem

Mutual wills create a binding contract, not just a shared intention. Once Selam's husband died having relied on her promise, the law treated her as bound: she remains free to sign a new will, and in fact she must, since her old will still names her husband as primary beneficiary, but whatever she signs is held to the original bargain. Courts enforce this through what is called a constructive trust — even if a later will said something different, the assets covered by the mutual wills agreement would still be treated in equity as belonging to the children, not to whoever her new will named. Selam's instinct that she could not simply write her children out, even if she wanted to, was correct.

The harder problem was Natalia's rights, which have nothing to do with the mutual wills agreement and everything to do with Ontario's family property law. Under the Family Law Act, a married spouse who survives the other has a choice: take what the will (or an intestacy) gives them, or instead claim an equalization payment, calculated by comparing the growth in each spouse's net worth during the marriage. That right exists regardless of what any will says, and regardless of any promise Selam made to a previous husband. If Selam died after marrying Natalia, Natalia could elect equalization and pursue a claim against the estate for a share of the property growth during the marriage — a claim that would come out of the same pool of assets the mutual wills agreement had already promised to the children. Two binding obligations, drawing on the same estate, each valid on its own terms and incompatible with each other in practice.

There was a second, smaller wrinkle Selam had also been carrying since she was married the first time under an older legal landscape: for years, Ontario law treated marriage as automatically revoking an existing will unless the will was made specifically in contemplation of that marriage. That rule was repealed for wills made or people who marry after a change in the law that took effect in 2022, but Selam's original will long predated that, and no one had ever confirmed for her which regime applied to her situation or whether her documents needed to be rewritten regardless of the answer.

What we did

1. Confirmed the mutual wills obligation and what it actually covered. We reviewed the original 1990s agreement and both spouses' wills to establish exactly which assets were captured by the binding promise and confirmed Selam's understanding that the arrangement survived her husband's death and bound her going forward, regardless of any new will she signed.
2. Clarified the will-revocation question so it was no longer a live risk. We confirmed that Selam's will needed updating in any event, both to reflect her new marriage and to make the mutual wills obligation explicit on its face, removing any ambiguity about which version of the revocation rule applied to her.
3. Explained the equalization risk to Selam in plain terms before the wedding, not after. The point we stressed was timing: a marriage contract negotiated calmly before a wedding, with both people willing to compromise, produces a far better result than the same conversation forced by a death and a grieving new spouse's lawyer.
4. Recommended a marriage contract (a domestic contract under the Family Law Act) rather than relying on the will alone. A will cannot override a surviving spouse's statutory right to elect equalization. Only an agreement between the spouses — signed with each side receiving independent legal advice — can validly limit or exclude that right.
5. Negotiated terms with Natalia's own lawyer. Natalia needed, and was entitled to, separate legal advice; a domestic contract signed without it is vulnerable to being set aside later. Over several weeks of exchanges, the two sides worked toward a structure both could accept.
6. Drafted a new will for Selam that worked alongside the marriage contract. The will named Natalia for a defined, limited share and preserved the bulk of the estate for the children, consistent with both the mutual wills obligation and the terms the marriage contract would set.

The outcome

The result was a compromise, not a clean win for either side, which is honest given what each person was legally entitled to claim. The signed marriage contract gave Natalia the right to remain in the family home for up to two years if she survived Selam, or a cash payment of roughly $150,000 if she chose not to, along with keeping her own separate retirement savings outside any equalization calculation. In exchange, Natalia gave up her broader right to elect equalization against the growth in Selam's other assets during the marriage, protecting roughly the remaining $1.65 million of the estate for distribution to the two children as the original mutual wills agreement had promised.

Neither side got everything. Natalia gave up a claim that, on paper, could have been worth considerably more if the marriage lasted many years and Selam's investments grew. Selam's children accepted that a modest, clearly defined share would go to their stepmother rather than the estate passing to them entirely intact, as the original 1990s agreement had envisioned before a second marriage was ever part of the picture. What made the compromise durable was that everyone signed it with full knowledge of the numbers and with their own lawyer's advice, well before there was a death, a funeral, or a grieving household to complicate the conversation.

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