Not with the Online version. The Online version is only good for one user, if you use your account to file someone's return, your information will be overwritten and you won't be able to get it back. You would have to create a new account (new useid and password) for additional returns with the Online version)
If they have a simple return, you could use the Free Edition. If not, for multiple returns you should use the Desktop version. You can unlimited returns to prepare, but you only get 5 Free Federal e-files, after that you would need to mail in your return. With Deluxe and above you get one Free State Software, there is a charge To e-file a State return.
https://turbotax.intuit.com/personal-taxes/cd-download
