What is the ruling regarding the marriage of a man who committed fornication with a Christian woman who became pregnant by him, then she embraced Islam after the marriage, and what is the ruling concerning the child born from that, and his other children with her?

The marriage contract is invalid due to her pregnancy from fornication, and the absence of the condition of two male witnesses and the requirement of the guardian (wali). The contract must be renewed by her Muslim guardian or a Muslim judge. The children are attributed to their father on whose bed they were born.