What are mutual wills and are they a good idea for blended families in Ontario?

Mutual wills are wills made by two people — usually spouses — under a legally binding agreement that neither will change their will after the first dies. They go further than "mirror wills," which simply reflect the same distribution plan but can be changed independently by either party.

For blended families, the appeal of mutual wills is that they can protect children from a prior relationship. For example, spouses might agree that both will leave everything to each other, and on the second death everything goes equally to all children from both relationships. The agreement prevents the surviving spouse from later changing the will to cut out their partner's children.

However, mutual wills come with significant practical problems. They can be difficult to enforce, and proving that an agreement existed and what its exact terms were can require litigation. Courts have upheld mutual will agreements in Ontario, but the evidentiary burden is high.

More importantly, mutual wills can create hardship for the surviving spouse, who may find themselves locked into a plan that no longer makes sense years later — for example, if their financial circumstances change or if a beneficiary named in the original plan dies. Alternatives such as trusts, life insurance, and clear will drafting often achieve similar goals with more flexibility. A lawyer can help weigh the options.