Fraud claim on property

What is available as a documentary proof only shall stand. All other matters that happened inter-personal outside the realm of documentation may not stand scrutiny or a Court case.

Without any proper documents for the transaction of money . you can not claim over it.

What was the version of your grandfather ?.  Unless there was a claim in the past, it is not proper to treat it a fraud.  Once a document is registered, the presumption is that the sale deed was executed only after receiving consideration, unless nonpayment of consideration was mentioned in the deed, with follow-up notices from the seller after such registration.

Your mother's right over the land is up to 25 decimal only as per the registered sale deed in her name.

This was the arrangement made by your grandfather by allocating 44 decimal to your maternal aunt and 25 decimal to your mother long ago when the property was purchased.

Your mother did not protest or object to this arrangement made by your grandfather at that time and accepted the same as per his decision.

Now what is the reason for this dispute?

Do you have documentary evidences to prove that your mother only funded for the entire purchase of this property?

If yes, then your mother shall first issue a legal notice demanding equal distribution or allocation of more land to her on the basis of the funds she had financed for purchase of this property.

If your maternal aunt is not agreeing for it then on the opinion of your local lawyer you can plan to institute a suit claiming the desired relief. 

Then you may have to file a Declaration suit praying the entire property belongs to your mother alone, within a limitation period and the court proceedings may take another one decade if you have all such documentary evidence that entire consideration.