The singer discovered that his civil rights pioneering great-grandfather was buried in a pauper's grave.
He said: 'We take so much for granted. This is about as close to a spiritual awakening as I've ever had in my entire life.'
Alabama-born Richie, 61, was stunned to learn that his great-grandfather was 50 when he married a 15 year-old, whom he later divorced.
And he became angry when he found out that his great-grandfather, J.L. Brown, had been 'owned' as a slave.
Former Commodores star Richie said: 'When we first started this journey I was always thinking we might uncover an ancestor like this [a slave owner], but this is unnerving in one respect, and empowering in another. It was an extremely brutal time.'