I grew up idolizing Sidney Poitier.

I was around 9 when he flickered into my world on a television replay of “Guess Who’s Coming to Dinner.” I was a latchkey kid in Cleveland, daughter of a white, single mother and a Black father — whose union their parents had frowned upon. In the film, Sidney and his co-star, Katharine Houghton, play an interracial couple whose parents also struggle with their children’s relationship. There I sat in front of my mom’s old console, mesmerized, as I watched my family’s dynamic play out. For the first time in my childhood, I felt seen. Understood. Validated. The world already knew Sidney, who died last week at 94, as a formidable performer. But I first experienced him as a mirror.

I watched that film over and over again, through my middle-school years and beyond. By then, my mother had moved our family from a...