1. One option is to create one account for the family that contains only the email address and subscribing that account to all groups the family members wish to receive messages from. Then, create separate accounts for each family member that only contains their cell phone numbers. Each family member can join just the groups they individually want to receive messages from. 
2. Another option is to simply add that email address to just one family member's account and ensure they are subscribed to any groups all family members wish to receive messages from. Then, the additional family members can have accounts with only their cell phone numbers.

(These same scenarios can also be used if a family shares a cell phone number, but have separate email addresses.)