If they were stealing from you to supply a drug habit, inflict physical harm, or cause serious emotional/mental pain. Then I could understand not wanting to be even a small part of their lives.
My brother and I have put our sister through drug and alcohol rehab 4 times in the past 6 years. But if she called tomorrow saying she was ready to try and get it together again, she knows Id be on the next flight out to help. We absolutely will have nothing to do with her, while she is drinking or high. Neither of us have heard from her for the past 6 months, nor even have a clue as to where she is.
Not saying you have to do every and anything they ask, but apparently its up to you to be the bigger person. Call your mom once a week. Call your brother once a week. It will most likely improve your relationships with them. If it does not work out, well heck you gave it a try. Good luck to you.