I have a couple brothers and they are not partners, but I think it helps when the customer can contact them when they are in charge of what they are doing.
more specifically, one brother does all billing. He can hand a biz card and no one has to call me regarding how much they owe, what dates were serviced. It helps me streamline.
The other brother does strictly mowing and manages all of one cities snow clearing activities. It has helped when customers want to know what time service will happen . I don't get called by people asking when someone else is going to do something. again it streamlines.
For the employees, it makes them feel important. It is a way to give a non-monetary raise.