As an administrator, go to Site administration > Users > Permissions > Define roles and click the "Add a new role" button.
If the parent has been given the Capabilities/tool/policy:acceptbehalf then they can click on the child's profile, click the Policies and agreements link and agree to the policies there:
This block needs to be added so parents can see links to their child's profile.
Once the mentees block has been added, a parent/mentor sees the link to any children/mentees they are responsible for.