Thanks for your response. Since my parents are going to apply for citizenship soon, they filed their taxes so they don't be asked why they haven't filed their tax returns. By the way, I called the IRS and I was told that since my parents had $0 federal tax withheld (line number 16), then they won't be qualified as a dependent. Now, I need to file an amend for them with the status of filling separately, so my brother and I can claim them as dependent. Thanks!
