Problems with defiant kids need to be addressed immediately because these issues do not get better with time. If your child is mean, vindictive and chronically disrespectful, then this is not a phase that he is going through. The fact that you have two kids who show this kind of behavior is not uncommon because siblings often learn from and mimic each other's behavior.
I understand that therapy for your kids is out of the question due to the expense, but I have an affordable solution for helping defiant kids change their behavior that has proven to be very effective in homes across the U.S. and Canada. It is an at-home behavioral program for kids called Total Transformation that shows parents how to teach their kids to treat others respectfully, make good choices and do their work at home and in school without resorting to harsh measures. This program works if you follow it. Just listen to the CDs and follow the simple instructions.