Why can a mother that never supported her child in any way, benefit from from his death?

My step-son was killed at the age of 16 by a drunk driver. He had an estate already set up and now we are having to go through the probate process. His bio-mother never paid a dime in child support and she would act as if he was a burden to her when he wanted to go visit her. Now that there is money involved - she is entitled to 1/2. So does any one know a way of keeping her from benefiting from his death? This is so not fair. I have documented in a diary everything that she has ever said and done toward him or us. We at one point had to get a no contact order against her because of threats she would make to him over the phone. She would say things like" I am going to come get you and no one, not even the cops can do anything about it". this scared him because she had abandoned him with some guy for atleast a week and he did not want to be with her because of that. This happen when he was 7 years old. We went to get him for the week end and found out that she had left the week end or so before and no one had any way of getting in touch with her. anyway, This is very upsetting to me to know that a deadbeat mother can actually benefit from her son's death, one that she had nothing to do with. Is there any law that can stop her from being entitled to 1/2 of his estate?

Please accept my sympathies. I assume that your son died without a will. He could have written a will and if he felt strongly about it could have cut mom out of the estate. Of course, few children have a will. BTW, life insurance proceeds are not part of the estate and are paid directly to the beneficiary.
When someone dies without a will, as they do every day, what happens next is determined the legislature. The legislature could have determined that each of those cases, the probate court should conduct a trial to determine the moral superiority of any surviviors, and to give the estate to the heir who was most deserving. No state or country has followed that path. Indeed the burden on the tax-paying public would be overwhelming as we would need a thousand times the number of probate courts and judges. So, the legislature simply picked a formula that they figured most people would want to follow if they had a will. Not all. Most. The other option would be unworkable.

As hard as it is, you have to let go of your anger against her. The law is clear; in the absence of a will, the estate is settled through probate, and blood-related parents will inherit, barring extraordinary circumstances.

The fact is you've lost something far more valuable than the estate; and the money will not bring her happiness or piece of mind. Once the estate is settled, this hateful woman will be out of your lives forever, and you will still have treasured memories of your son - that's worth more than any estate.