Check Out the Investors You Haven't Considered YetWealthy families have money to invest. Here's how to find it.

When Morten Middelfart went searching for seed investors for Social Quant, his Twitter analytics company in Tampa, Fla., his banker suggested pitching Atlantic Merchant Capital Advisors, a local family office. One informal meeting with the private investment firm, which manages the wealth of individuals and their families, was all it took to land Middelfart's venture a high-figure investment early this year, along with ongoing advice, customer introductions and part-time office space.

Such experiences are rare, but they do happen, and more family wealth-management groups are betting on private equity deals. There are some drawbacks: Family offices can take longer to seal the deal than traditional angels and VCs, and they generally have a lower tolerance for startup failures, warns David McCombie III, CEO of McCombie Group, a Miami-based private investment firm that has invested about $10 million in half a dozen startups in the past three years. But, he adds, many enjoy advising and supporting founders beyond simply writing a check. Plus, they have buckets of cash.