Provisions of Section 11 of the Hindu Marriage Act lays down the consequences of marriages within the prohibited degree of relationship:
Section 11. Void marriages.
Any marriage solemnised after the commencement of this Act shall be null and void and may, on a petition presented by either party thereto against the other party be so declared by a decree of nullity if it contravenes any one of the conditions specified in clauses (i), (iv) and (v) of section 5.
As such, the marriage is null and void and either party (husband or the wife) could get the marriage declared void; but for this limitation, such marriages are true and valid against the whole world and the children born, legitimate. There is nothing in the Marriage Act or any other law which decalres such marriages to be illegal or unlawful or a penal offence or invites any other adverse civil or penal consequences. And, to be knowledge, there is no law enacted or rule notified under the provisions of Article 309 mandationg that the Government servant who has married within such prohibited degree to have committed a misconduct and hence liable for departmental or disciplinary proceeedings and punishments, as provided.