“A millionaire sees his ex-girlfriend begging on the street with three children who look exactly like him—what happens next will break your heart.”

It was a frigid December morning in downtown Chicago when Ethan Wallace, a 35-year-old tech millionaire, stepped out of his Tesla to grab a coffee before a business meeting. He was checking his emails when something on the sidewalk stopped him in his tracks.

There, seated against a brick wall, was a woman with matted hair, a tattered coat draped …