There are family trees … and then there are genograms. A genogram goes beyond names and birth dates to chart information about relatives’ relationships with one another, their physical and mental health, and the places where they grew up. “It’s an amazing way to map who you are and where you come from,” says Monica McGoldrick, a family therapist who has helped popularize genograms through books like “You Can Go Home Again.” The charts make it easy to recognize family patterns you may have never thought about: entrepreneurial success, disease or marital longevity.

The holidays, when far-flung families reunite, are a good time to get started. First, download software for your project at genopro.com (free for fewer than 25 people; $49 for 26 or more). Then fill in as much information as you can on your own.

Before packing your laptop for Grandma’s, warn people about your project. “It’s important to tread lightly,” says Raeann Hamon, a professor of family science at Pennsylvania’s Messiah College, who typically arrives at family reunions with a microcassette recorder in hand. In interviews, start with basic questions, then hope your subject yields much more. You may walk away with a new sense of identity.