Family offices have tripled since 2019, creating a new gold rush on Wall Street

A version of this article first appeared in CNBC's Inside Wealth newsletter with Robert Frank, a weekly guide to the high-net-worth investor and consumer.  Sign up  to receive future editions, straight to your inbox.

The number of family offices in the world has tripled since 2019, setting off a new race among private equity firms, hedge funds and venture capital firms to attract their investments.

According to a new report from Preqin, the number of family offices — the private investing arms of wealthy families — topped 4,500 worldwide last year. North America has the largest share of family offices, with 1,682. More than half of all the family office assets in the world are in North America.

Experts say family offices now manage $6 trillion or more, and their ranks are growing. There are more than 2,600 billionaires in the world, almost all of them requiring a family office. And the number of people in the world worth $100 million or more — the typical threshold for a family office — has surged to more than 90,000, according to Wealth-X, an Altrata company. In other words, there is more room to run.

The family office boom has caught the attention of private equity firms and other alternatives managers who are looking to raise funds. Blackstone, KKR and Carlyle have all been expanding their teams, funding events and building products catering specifically to family offices.

"The larger private equity managers are trying to compete there by putting in resources and time," said Rachel Dabora, research insights analyst at Preqin. "Ultra-high-net-worth investors and family offices are really on their radar."

On the surface, family offices are dream clients for alternatives. For years, family offices sought basic wealth