FAISALABAD, Pakistan — Nasir Dhillon, a former policeman, sells houses in a Pakistani city about 100 miles from the Indian border. His real estate company has four locations and he drives a Toyota SUV, a local marker of affluence.
But Mr. Dhillon, 38, is better known for his sideline: reuniting people separated from their relatives during partition, when Britain split its large South Asian colony into Hindu-majority India and Muslim-majority Pakistan in August 1947.
Mr. Dhillon is the…