My spouse and I are helping my step son with a portion of his college expenses. He is currently 19. My question is, can my step son petition the court for chlid support from his father, since is refuses to support him in any way.

The step son cannot petition for child support on his own behalf; the other parent would have had to have done that while he was still a minor.

Child support in California ends at 18 and graduated High School. After that without special circumstances ( medical reasons ) its not mandatory.

Thank you for the responses. This helps a great deal.