"5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child."
This essentially means that you have the parent’s permission to claim the child, if the child also lived with the parent more than half the year.
There's actually two more rules:
8. If the parents of a child can claim the child as a qualifying child but no parent so claims the child, no one else can claim the child as a qualifying child unless that person's adjusted gross income (AGI) is higher than the highest AGI of any of the child's parents who can claim the child.
9. The "child" must not file a joint return with his spouse.
