You could go for "Google Family link", will let you know of your family member's location, when they leave or enter a certain location as well as live location, also it wont require your phone number, just simply the gmail. Only catch is, is that it is desgined as a parent child format, so it may not be up to standards if used for siblings or elderly, i suggest you have your go at it and use it if it manages to fullfil your needs