My brother made a mistake and claim himself on his tax return. I put him as dependent because he qualify. Can he amend his tax return? How long would the process take?

[Texas Roger]

Yes he must amend his tax return to indicate that someone else can claim him as a dependent. The amended return form 1040X must be printed and mailed and will take 16 weeks or so to get processed. Here are instructions for amending a return: 

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed

To claim your brother and file your return, you must print and mail it because his amended return will not be processed and the IRS database changed in time for you to efile your return. 

[macuser_22]

Amended takes about 4 months.  You would have to paper file this year if you can claim him.