In Islam, if a woman’s father is unavailable or deceased, her Wali (guardian) for the marriage contract becomes the next closest male relative in this order: grandfather, adult brother, paternal uncle, then male cousins. If no qualified male relative is present, a qualified Islamic judge becomes her Wali.

1- It is not essential to take shahadah (say the testimony of faith) before witnesses. Islam is a matter that is between a person and his Lord. 2- No marriage contract is valid without a wali (guardian) for the wife, but no non-Muslim can act as a wali for a Muslim woman. For more, see the detailed answer.