The 54-year-old actress discovered royal lineage in her background, and learned her great-grandmother Maria had her grandmother Angelina out of wedlock. Maria married Bertinelli's great-grandfather Francesco two years after she had Angelina, but was widowed the year after the wedding.
"Valerie Bertinelli goes down her father's side of the family and then she goes down her mother's side of the family, which she knew very little about," executive producer Dan Bucatinsky told The Wrap. "In a way, we were able to sort of satisfy curiosities on both sides of her family and in really satisfying ways, emotional, intriguing, things that she knew nothing about that are complete surprises to her."
Bertinelli also discovered Maria's second husband, Gregorio, attempted to murder her great-grandmother, and believed her dead before he committed suicide. Several other celebrities have learned of murderers within their families during the season, and Bucantinsky said the trend was "not intentional."
"It wasn't a theme we were going after, but it just happened to happen," he said. "It's interesting that there are common themes that emerge but are certainly not what we are after. We don't do it with that intention. It also goes to show how much commonality there is in all of our lives."
Who Do You Think You Are? is in its second season on TLC, and previously aired for three seasons on NBC. Season five has featured Bertinelli, Cynthia Nixon, Jesse Tyler Ferguson and Rachel McAdams thus far, and Kelsey Grammer and Lauren Graham's episodes are yet to come. Grammer's episode will air August 20, while Graham's is scheduled for August 27.