When my father-in-law, Leonard, passed, his will forced us to live together for a year—attending daily family dinners or losing the inheritance. To enforce it, he hired Mr. Morrison.

At first, dinners were tense, but soon secrets unraveled. My daughter Katie blurted, “Mom’s letters weren’t for Dad.” Then Evelyn, my mother-in-law, declared, “One of your children isn’t family. A DNA test will prove it.”