I have the conviction that you can and must keep secrets from your enemies because they will use every information to harm you. That's the justification to keep the order hidden, for instance and the identity of each of the templars a secret: protection against enemies. But you should not keep secrets from friends, family, spouses, loved ones. You must be open to them and tell everything to prepare them, make them able to deal with trouble when it arises and PROTECT them from the emotional effects of having a hidden secret disclosed and trust harmed. Secrets kept from loved ones are always toxic, and the damage is produced not because they are disclosed but because they were kept in first place. Secrets are a commom plot device in fiction just because they will demand a lot of resources from protagonists to be kept, it will stress them, consume mental energy and put them in conflict and after the reveal there will be the devastating effect on those who were kept in the dark and had their trust destroyed. So, keep secrets to protect someone? OK. But from enemies, not from beloved ones.