One of the 3 is usually the Boss in some capacity. What that means, is that the 2 junior pilots will do most of the flying. The Boss will take the day trips, and the flights with the aircraft Owner. If the airplane will fly 300+ hours a year, 3 crew is tough, but 3 is a necessity on just about any airplane, someone may get sick. Owners don't want to talk about Pilots with the sniffles.