In your case the relationship certificate and death certificate is enough for selling the land.
A succession certificate, issued by the court after necessary investigation, establishes who the legal heirs are and grants them the authority over the debts, securities and assets of the deceased. It also mentions the relation of the petitioner with the deceased, details of other surviving legal heirs, the time, date and place of death of the deceased and that the deceased died intestate.
If needed please go through the steps for obtain a succession certificate .
Application:
A petition needs to be filed with the district court or high court within whose jurisdiction the asset is located.
Application for such a certificate shall be made to the District Judge by a petition signed and verified by or on behalf of the applicant in the manner prescribed by the Code of Civil Procedure, 1908, (5 of 1908.) for the signing and verification of a plaint by or on behalf of a plaintiff, and setting forth the following particulars, namely:--
(a) the time of the death of the deceased;
(b) the ordinary residence of the deceased at the time of his death and, if such residence was not within the local limits of the jurisdiction of the Judge to whom the application is made, then the property of the deceased within those limits;
(c) the family or other near relatives of the deceased and their respective residences;
(d) the right in which the petitioner claims;
(e) the absence of any impediment under section 370 or under any other provision of this Act or any other enactment, to the grant of the certificate or to the validity
thereof if it were granted; and
(f) the debts and securities in respect of which the certificate is applied for.
Details: The name and relationship of the petitioner, names of all heirs of the deceased, details about the time, date and place of death should be mentioned in the application. A copy of the death certificate has to be produced.
Process: The certificate is granted by a competent civil court after you file an appropriate petition mentioning the details of legal heirs, property etc. The court will thereafter issue notices to all the legal heirs to attend the proceedings. The court typically issues a notice in the newspapers for a given period (generally 45 days). If no one contests the petition on the expiry of this period, the court passes an order for issuance of succession certificate.