If using the "Online" software...yes.
BUT
You must have an entirely new UserID/Pwd in a separate Online account for the sibling. And if they used TTX Online last year, the sibling should already have a separate account you should use...talk to that sibling to make sure whether they did or not.
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IF, instead, you are using the "Desktop/Download software", then you can start a New tax return as a simple menu selection. Desktop/download softwre allows you to prepare as many tax returns, for you and yoru family, as you need, but only 5 can be E-filed. Any attached State tax returns can also be e-filed, but that costs an extra $20-$25 to efile (except for NY )...though printing and mailing the state yourself would be free.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
