Succession opens on date of death; by inheritance or by testamentary succession (by valid WILL).
A registered WILL should be a valid WILL.
In case of Hindu male dying without disposing her estate/property in her life time by a valid/registered deed the 1st right is of ClassI legal heirs ie.e Mother (if alive as on date of death), Wife (if alive as on date of death), sons, daughters…… Thus, in query posted by you, if said property of father of X was self earned/acquired and also if mother of father of X and wife (of father of X), both were not alive as on date of death (of father of X) then only X could become sole survivor and hence sole owner by inheritance. If said property of father of X was ancestral then only his share shall devolve upon X.
In case of deceased Hindu woman dying without disposing her estate/property in her life time by a valid/registered deed ClassI,II is not applicable rather nature and source of property matters.
If the property is self acquired/earned/absolute in the hands of Hindu woman the 1st right is of her husband (if alive as on date of death) and sons, daughters…………
If property is acquired from husband side 1st right is of her sons, daughters…………and if sons, daughters are not available then legal heirs of husband..
If property is acquired from parents side 1st right is of her sons, daughters…………and if sons, daughters are not available then legal heirs of father..
Thus if Mother of X was owner/title holder then you can determine ( as explained above also) X could be the sole owner by inheritance, if X sole surviving legal heir.
The authority under whose jurisdiction property falls has a set procedure for such matters if the WILL has surfaced; Testate Succession…….and the prescribed forms, procedure, process is available in O/o Authority and even on website. Certified copies of the WILL, death certificate, legal heir certificate/affidavit (per local procedure/precedence) are basic requirements. The authority may ask for NOC from legal heirs (other than beneficiary) and/or to release newspaper advt and/or may write to legal heirs to submit their objections if any within set time.
If there is NO contest to the WILL by any legal heir then authority shall act upon the WILL without any cloud on it and transfer the ownership in the name of beneficiary.
If WILL is contested it lands up in probate court of pecuniary jurisdiction. The court shall decide on validity of WILL.
The legal heirs may also consider perspective of registered family settlement after the WILL and register it.
Check locally and comply with procedure. Thereafter concerned official in the O/o Authority e.g; Patwari, shall act upon the matter and transfer the ownership by inheritance/probate in the name of legal heirs in mutations records.
Thereafter obtain copy of updated mutation records.
For partition by boundaries either decide amicably (best recourse) or take help of other elders of the family or panchyaat or court of law..
If WILL is not submitted to be acted upon then it becomes matter of succession per personal law that applies.
Although it is wrong since the WILL exists.
Check locally and comply with procedure.