A binding contract under which two or more people — often spouses in a blended family — agree to make their wills in agreed terms and agree not to change them without the others' consent. Its purpose is to ensure that, after the first person dies, the survivor cannot rewrite their own will to defeat the agreed distribution. If the survivor tries to do so, the intended beneficiaries have a legal basis to enforce the original terms.
Mutual wills are particularly useful in second marriages, where one spouse wants to provide for the other during their lifetime while ensuring that property ultimately passes to children from a previous relationship.