NOC from another legal heir to sell property

Flat owner died without making a will. Subsequently, his wife also died. Thereafter their two sons, being the legal heirs furnished Stamped Affidavit to the Co-op. Hsg. Soc. (under Maharashtra Co-op. Hsg. Soc. Bye-laws) conveying their no objection to accept one of the brothers named therein as a member of the Society, with further declaration that no other legal heirs are left behind by the deceased and that they agree to indemnify and keep indemnified the Housing Society harmless against any claim, demand, suit or any legal proceedings which may be filed by any person or persons claiming either lawfully and / or equitably through the through the deceased flat owner. Based on the Affidavit and Undertaking (submitted as per Society Bye Laws), the Society transferred share certificate in the name of the named legal heir and accepted him as a Member of the Society. The question is for selling the said flat now, whether the said Member alone can execute the documents as a seller or his brother should also join as a seller since he is also a legal heir. It is relevant to mention that the buyer is not insisting for the Member's brother to join and execute documents as seller. Hope even if the Member alone executes the documents as a seller, the title gets properly passed on to the buyer.