When Should Children be Responsible?

Question:

I just found this sight and I already feel so relieved that you may be able to help. I already read e-mail about 10yr old “forgetful” girl. My question is how responsible can I legitimately expect my 10 yr old step-son to be. I believe he “forgets” to do chores right or brush his teeth etc. because he gets special undivided attention when he is getting in trouble even though it is negative attention. He is a very intelligent boy. His biological mother is rarely in the picture and constantly lets him down never making him feel important and I think he is replacing that much needed good feeling with all negative attention.

We have issues every single day of him “forgetting” to do everything. He refuses to take any responsibility or accountability for his actions. His regular response is…”uh I forgot”. We have tried the special time for him, giving him less responsibility, grounding him, taking his things away etc. but you see his biological mother is constantly letting him down every time we are able to build him up even just a little bit. Since I have no control over that how do I get any kind of consistency when there is always a new issue with her?