So in this case, the teenager might already have their own teamstuff login, including teams, schedules and a profile. If they want to, they can now invite as many parents as they want to share access to these teams and schedules.
To do this, you need to login to;
1. Jump onto teamstuff on the web
2. Login as the teenager ( of course )
3. Navigate to the profiles - they should see only one ; the 'me' one like below
4. Now click on the icon on the far right - shared access
This is the section that shows which other teamstuff users ( adults ) have access to seeing this teenager's teams, games and details. So to add Mum for example, just;
5. Click on the little 'plus' icon on the left near the word Share,
6. Add Mum's email and we're done.
Mum will get an email invitation, which they should click through to accept the shared access. The child's profile will then appear in Mum's set of profiles, and all games/teams will be visible too. Note also that teamstuff understands the relationship properly - so if Mum changes her email or phone ; that automatically propagates across to the child profiles she has shared access to.