It's good to plan things ahead instead of waiting for something to happen. That's why the greatest mistake is the one you're not prepared for. First it's not bad to share your passphrase with your family but it must not be with all your family members. At least you should have one person that you trust. By that you create a clear plan with him or her to know exactly what they should do with the passphrase incase of emergency purpose. Even if the person doesn't know what a passphrase is just tell him or her to keep it in a fireproof safe or a vault because the goal is to protect it from physical damage or any unauthorised access of the passphrase.