In March 2008, I was 13 when my dad and I watched the TV miniseries “Roots,” which follows the fictional story of a man born in 18th century Gambia who is sold as a slave in America, and the many generations who come after him. It inspired me to ask questions about my own family’s past. Suddenly I started searching online, interviewing older relatives, and exploring libraries and archives. Surprisingly, more than half of Americans can’t name all four of their own grandparents, and over 20% of black Americans have never looked into their family tree. But, as a result...