If someone who is not a member of our Google Nest "household" is accessing one of our cameras, then Google Nest has a serious undisclosed security hole that is allowing that to occur.
I haven't seen anything in the Google Nest app or Google Home app that shows or tracks who is viewing our cameras. I'm guessing this is because such viewing should only be possible by a member of our "household".
I hope we were able to answer your question with the info provided by @MplsCustomer. If you have additional questions, feel free to respond to this thread and we'd be happy to further assist you.