you friend has right to file a criminal complaint against all of them u/s 4 of Dowry Prohibition Act before police or magistrate as case may be.
read the section carefully
4. Penalty for demanding dowry. If any person, after the commencement of this Act, demands, directly or indirectly, from the parents or guardian of a bride or bridegroom, as the case may be, any dowry, he shall be punishable with imprisonment which may extend to six months, or with fine which may extend to five thousand rupees, or with both: Provided that no court shall take cognizance of any offence under this section except with the previous sanction of the State Government or of such officer as the State Government may, by general or special order, specify in this behalf.