The MacNaughton-Kobayashi pairing is such a family affair that it’s not surprising the marriage would produce a “child” — BlackSand Capital — and one that can serve the purpose of the parents, too.

BlackSand is a private equity firm that puts together funds, acquires a development asset and makes money for the investors. It can supply some of the money needed for projects engaging MacNaughton and Kobayashi, but other partners as well. The bonus, say its principals, is that because most of the capital comes from Hawaii investors, the gains tend to stay in-state, too.

It’s run by B.J. Kobayashi and Ian MacNaughton, scions of the longtime partnership firms. The niche is financing Hawaii-based projects, a process that can be easier and faster for a locally based equity company to navigate.

After law school, Kobayashi was drafted by his father to put together capital for the larger projects the construction firm wanted to do. Ian MacNaughton returned to Hawaii after working for the Swiss investment banker UBS, Goldman Sachs and Starwood Capital Group.

“That’s when I first began thinking about doing it here in Hawaii,” he said. “Because Ian would make a great partner, because he’s worked in the business. I did not work in the business; I worked a lot across the table from them, but I was not inside the belly of that beast.”

Not everyone’s related in the family enterprises. Kathryn Inouye is a partner at Kobayashi, for example, and Dick Gushman, Jeff Arce and Eric Tema are among the many names mentioned at MacNaughton offices. But just rounding out the family roster, brother Brett MacNaughton is a development associate focused on design, and sister Alana Kobayashi Pakkala is executive vice president and marketing director.