Based on your question I assume you're using Nest Thermostat (2020) with the Google Home app. Unfortunately, adding members to your home means they have the same access and control as you. The only way to prevent what you described is to remove them from the home. This is mostly a user to user community, therefore if this is important to you, I’d encourage you to also send this feedback directly to Google. You will not receive a response, unless Google need more details from you, however the team are still reading the feedback.