Booknetic is a system with Group Appointments feature. If the service is a group service, more than one customer can make an appointment for the same timeslot.
If your customers do not want to come alone and bring someone else with them, they do not need to make a separate appointment for each person they bring. Your customer can choose how many people to bring with them with the "Bring people with you" feature.
For this option to be active, you must first set your service capacity as Group. You can also specify the maximum number of people for the timeslot.