David Cook's tears at the end of his brilliant American Idol performance on Tuesday night were triggered by the special guest who came to see him perform this week.

David's brother Adam, who is battling brain cancer, traveled from Indiana with a medic and a nurse to see David's rock-tweaked rendition of Mariah Carey's "Always Be My Baby." When David sang lyrics like "You'll always be a part of me," we couldn't help but wonder if he was singing for Adam, whose condition has worsened in recent weeks.

People magazine reports that David went to Adam's seat and hugged him when the show went to commercial break. More about the story at People.com.