Can I use one account to file 3 seperate returns for three different people?

No.  Or you will overwrite the previous return.  

Online is only good for 1 return per account.  But you can use the same email address for 5 accounts.  You can start another return in TurboTax Online by:

1. Logging out if you are in your account
2. Choose what TurboTax Online product you want to use for the second return
3. Create your account screen
4. Set up a new login for the second return
5. Start working on the new return

The Desktop program can do unlimited returns and efile 5.  You can buy the Desktop CD/Download program at

TurboTax® 2021-2022 CD/Download Tax Software, Compare Desktop Tax Preparation

Using the online version you can only file one return per account. The other 2 would need to open their own online accounts. However if you had the download version you could file up to 5 different returns using the same program.