You cannot file your family member's taxes from your own account. You have to create a new account for them and report their information under their new account.
See instructions:
Sign out of TurboTax Online.
Select the TurboTax Online product you want to use for the second return and proceed.
On the Create your account screen, set up a new login for the second return.
o You can reuse your email address if you want to receive e-file notifications for the second return.
o Up to 5 accounts can be tied to the same email address.
After you've created the new account, you can start working on the second return.
Tip: If you're preparing multiple returns for family members, it's more economical to switch to the TurboTax CD/Download software, which lets you e-file up to 5 federal returns at no additional cost. More info
