My cousin passed away with no will. He had no wife,no kids, and no siblings. Ca. attorney sent a letter stating that since there was no will... the estate is split 50... 50 to his mother and father. Both are deceased and died prior to my cousins death. The father's portion goes to our family. The mother's portion goes to the state of California since there are no family members found from her side. These parents were divorced decades prior to their deaths. I'm confused. Can you please tell me where that is written in the law books?

This is covered by Probate Code Section 6402.5

California Probate Code Section 6402.5 - California Attorney Resources - California Laws

Paragraph 3 is what you are looking for.