On iPhones, you can have your phone on Do Not Disturb but allow Favorites and/or repeated attempts through. You can also set specific people for Emergency Contact, which will let them reach you no matter what. You could put a different ringtone on those people to let you know it’s one of them.

https://www.howtogeek.com/436750/how-to-let-a-contact-bypass-ios-do-not-disturb-mode/

Android may have something similar.