S.W.
Try telling him the truth. Look him straight in the eyes and tell him that Mommy and HIS baby sister love him and both thinks he is the greatest big boy in the world. Ask him if he can help Mommy change her by getting the diapers or something because he is Mommy's big little man. Every one needs to feel wanted and appreciated for their strength and greatness. It starts as we are children. Tell him how great he is -as he is- not what you want him to do. Give him some time with this technique. I have a 4 year old daughter and she is very independent. It is the only way I get her to do ANYTHING! Also as a Licensed Professional Counselor - I tried basically every theory in the textbooks...So far this is the one that works best for us. This one came from the Basic Instuction Book for Life Events. I refer to it for everything.