Maybe. They don't have to file if they only have W2 income under 14,600 (2024) but can file to get back any withholding taken out in boxes 2 or 17. But you don't get boxes 4 or 6 back. If they got a 1099Misc or 1099NEC they have to file it as self employment income no matter how small the amount.
Online is only good for 1 person and 1 return. To do another return you need to set up a new account. You can use the same email for 5 accounts. If you have the Desktop program it can do multiple returns and efile 5 for free.
Be sure on their return they check the box that says they can be claimed on someone else’s return.
You can start the Online Free Edition here,
https://turbotax.intuit.com/personal-taxes/online/free-edition.jsp
Filing requirements for a dependent
https://ttlc.intuit.com/community/children-dependents/help/do-i-need-to-file-my-own-taxes-if-i-m-a-dependent/00/26111