Due to the way HomeKit works, a single HomeKit device (like Starling Home Hub) can only appear in the HomeKit home it’s physically located in. This means, for example, that a single Starling Home Hub cannot place some devices in one HomeKit home, and others in a separate HomeKit home.
As a convenience feature, by default Starling Home Hub imports devices from all Nest homes in your account into your selected HomeKit home. For many customers, this avoids the need to purchase another Starling Home Hub for a second home. If you want to import Nest devices from only one home into HomeKit, then go to the Starling Home Hub app, Hub, Home and Product Settings, press All Homes and then select the home you want from the drop-down.
If you have two homes, and you want Nest devices physically in home #1 to appear in HomeKit home #1, and Nest devices physically in home #2 to appear in HomeKit home #2, you will need one Starling Home Hub in each home. Both Starling Home Hubs can be signed into the same Google/Nest account without any problems.
If you have any other questions about usage with multiple homes, please contact Starling Support with a detailed description of your set-up, and we'll advise what configuration is most suitable for your situation.