Yes, based on the facts stated by you, there is a legal possibility of challenging the settlement deed, but its success will depend on the evidence you are able to produce.
If your father executed the settlement deed while he was intoxicated, illiterate, and did not understand the nature and consequences of the document, and your brothers procured his signatures by fraud, undue influence, or misrepresentation, the settlement deed can be challenged before the competent civil court. The same applies if your illiterate mother was made to sign without the contents being explained to her.
The facts that may strengthen your case include:
- Your father was allegedly an alcoholic and intoxicated at the time of execution.
- Both your parents were illiterate and unable to understand the document.
- The settlement deed was executed without informing either of the daughters.
- Your brothers allegedly assured you for several years that they would give you your share, thereby inducing you not to take immediate legal action.
- Your sister is a person with disability.
- You and your sister were the primary caregivers of your parents and bore their medical expenses, for which you have documentary proof.
However, merely proving that your parents were illiterate or that your father consumed alcohol will not, by itself, invalidate the settlement deed. The court will require evidence showing that they did not execute the document voluntarily or that it was obtained through fraud, coercion, undue influence, or without understanding its contents. The burden of proving these allegations lies on the persons challenging the deed.
Another important aspect is limitation. Since the settlement deed was executed in 2017, the court will examine why it was not challenged earlier. You will have to explain that your brothers repeatedly assured you that they would honour your parents' wishes and give you your share, and that you discovered their refusal only after your father's death. Whether this explanation is sufficient will depend upon the evidence.
If the settlement deed is ultimately set aside, the property would ordinarily devolve in accordance with law, and as daughters you would also be entitled to your lawful share in your father's estate. If the settlement deed is upheld as valid, your claim against the settled property would become difficult.
Therefore, if you genuinely believe that the settlement deed was procured by fraud or undue influence, you should immediately consult a local property lawyer and institute a civil suit seeking cancellation/declaration that the settlement deed is void or voidable, along with consequential relief regarding the property. Delay should be avoided, as limitation and third-party rights can complicate the matter further.