Notary attested stamp papers is valid or not

Sir I hv Question. My father expired. We are four brothers. My brothers are saying u had signed in A notary attested stamp papers u hv no share in this house. My father was Very strict. I had given my total all income to my father not A single peny to keep me. He gives us some amount to our Expenditure. They told that time (sign here ) on any paper or any cheque book then i do, i didnot ask anything that time but this time my brothers are taking advantage of this my foolishness. I want to ask is notray attested paper is valid or not. & what i hv to do now.