Most rich people don’t stay rich forever.

About seven in 10 wealthy families lose their fortune by the second generation, according to a study of more than 3,200 high-net-worth families by the Williams Group wealth consultancy. By the third generation, that number has jumped to 90 percent.

Michael Cole — the president of Ascent Private Capital Management at US Bank, who has worked with clients worth $75 million or more for decades now — says he knows why. Often, “it’s because of failures in trust and communication between family members,” Cole says. “Wealth [often] breaks down family trust and relationships.”

Specifically, Cole, whose new book “More than Money” is out today, says he believes that about 60 percent of the wealth disintegration is due to a lack of communication and trust; 25 percent to a lack of preparation for how to handle the money; and about 10 percent to a lack of a shared vision about family goals around money. Bad investment and financial decisions tie into all of these too, of course.

Cole says one big issue is that many people feel that money is taboo to talk about, and so they don’t. He had one client who lived simply, but had amassed a roughly $100 million fortune that he was going to give to his three daughters. He hadn’t told them a thing about it. And when he died, there was a “feeding frenzy” of people wanting things from them, he says. “They were never prepared for it,” he says.

Often too, the second and third generations — who have been raised wealthy, and thus much differently than the person who made the money to begin with — behave differently, and that hurts the family fortune. “The people who created the wealth were often obsessive,” Russ Prince, president of the wealth research and consulting firm Prince and Associates, told CNN a few years back. “But their kids were not hungry.”

Whatever the reasons fortunes get squandered, Cole says there are a number of things rich families can do to stay rich. These include having conversations to determine how to manage the family money, discussions about the roles each family member should play, and a shared family mission statement about what the money means for their lives.