Hi there -
Our scheduling API support booking group appointments for Millennium implementations using Revenue Cycle Scheduling. In these instances, for your example, each of the three participants will have an appointment with the same location, provider, appointment type, start time and end time. For aggregating, if you match appointments that match all of those criteria, I think it would be safe to denote them as a group appointment. I would recommend working with your Cerner host client to get a list of appointment type ids that they have configured as group appointments, so that you can also use that identifier as a cross reference.
In a group appointment, each patient will have a unique appointment and slot id, we do not use the same appointment id with multiple patient participants.
We do not have an API that would allow a consumer to retrieve only group appointments.
-Richard