By "3 different homes" do you mean 3 different physical homes each with its own Wi-Fi network, or do you mean 3 different Google Nest "homes/structures" under 1 Wi-Fi network in 1 physical home?
If it is the former, you can't do it. A Nest Aware subscription covers all of the Google Nest devices in the same Google Nest "home/structure" on the same Wi-Fi network.
If it is the latter, and you want to move your Google Nest devices from 3 Google Nest "homes/structures" into 1 Google Nest "home/structure", the instructions for moving cameras and doorbells is below:
These are the instructions for moving other devices:
Awesome, glad to hear! It looks like we can consider this one complete, so I will be locking this in 24 hours if we won't hear back from you again. Feel free to start a new thread and we'll be happy to help.
Thanks for the help, MplsCustomer.