While nearly two-thirds of family-owned businesses reported growth in the past year, many are still preparing for the worst, a new survey shows.

Among 89 companies where more than half the shares are held by a single family, 84 percent said they've made provisions to cope with the death of a key manager or shareholder, according to PricewaterhouseCoopers.

"One reason for the high percentage may be that the future of the estate tax has been a leading topic of political debate, forcing companies to plan ahead to minimize the tax consequences of passing the business to the next generation," Alfred Peguero, the head of U.S. family services at PricewaterhouseCoopers, said in a statement.