Duncan and Cody have both had some huge changes occur in their lives. They both need some time to figure it all out. What you are going through is perfectly normal. If at all possible, it is best to let the two little boys figure it all out on their own. The worst possible thing you could do would be to scold one in front of the other.
You need to be sure that YOU are the established leader and then Duncan and Cody will take their cues from you.
Both the dogs might be picking up on your stress -- so the best thing you can do is to relax a bit
