If you want to change a Spond user from a member to parent/guardian, the group admin can do this. If you're not an admin, please ask your group admin to do this for you.
The admin needs to remove the contact points (email/phone number) from the member, and place them where it says 'Guardian' for the member
If a guardian wants to be a member of the group, the admin can add the person as a new member, with the same contact information that the guardian used to register in Spond.