Hi. This would be unacceptable to me, and most people I bet. It is on your partner to handle this. He needs to talk to them and set boundries, such as the key is only for emergencies. If after that, they don’t respect the rules, it is locks changed and a key given to a trusted friend, again only for emergencies. This is a gross invasion of privacy. If your husband won’t put a stop to it, might it become a “deal breaker”? It would be for me.