The next time you’re at the airport or checking into a hotel, you might notice a traveling group that looks, at least at first glance, a little unwieldy: young kids, their parents, and their grandparents, all vacationing together regardless of age or mobility limits.

A scene like this would have been rare a few decades ago, according to Susan Rugh, a history professor at Brigham Young University who wrote about the history of family travel in her book Are We There Yet?: The Golden Age of American Family Vacations.

The classic 20th-century family vacation was typically a nuclear one, comprising a mom, a dad, and their young kids. Grandparents and other relatives seldom came along. But more and more, research shows, families tend to bring multiple generations with them.

This, in turn, has changed people’s preferred travel destinations, and even the very purpose of travel: Multigenerational groups are much more likely to take simple, relaxed beach vacations than to embark on logistics-heavy city visits or road trips.