There are 2 numbers that regulate the number of people onboard. The number of guests for daily charters and the number of guests for overnight charters. We have seen some flexibility for kids under 12 months. Nevertheless, there are serious bureaucratic, legal and insurance limitations and the yacht managers definitely are on the safe side.
Usually, the issue is resolved by getting a boat with more sleeping space (similar boat with Pulman beds), getting a bigger boat, getting 2 boats or adjusting the number of guests.