Before we go any further, how did he arrive here?My stepdaughter has recently married her undocumented boyfriend. The primary reason for getting married was to help him gain US citizenship.
Did he arrive legally (say, on a tourist visa), and simply overstay?
Or did he enter illegally?
If the latter, your entire question is moot. He cannot change his status via marriage, as he has no status to change. Green card and citizenship are right out until he goes back to his country of origin and waits for a proper visa.
If the former, then you need to speak with an attorney, because if the child's father is here in the US, but not on the MediCal paperwork, the state could make a pretty good case for fraud against your step-daughter.

