Go to the following link for instructions to amend a 2020 tax return that you filed with TurboTax.
How do I amend my 2020 return?
When you make the changes for the amended return, all you have to do is check the box that says someone else can claim you.
It normally takes the IRS 16 weeks to process an amended return. But they are severely backlogged this year, so expect it to take much longer than that.
Don't file the amended return until you have received the refund from your original return.
However, even after you file your amended return, your brother will not be able to e-file his 2020 tax return. He will have to print his tax return, sign it, and file it by mail.
