Can we get back our property

We are 6 family members 3 brothers and 3 sisters, one of my brother had sold my ancestral property with 1/6share each to buyer on ₹500 stamp paper on sale agreement for ₹2850000 written on stamp paper we have received this amount in cash , I myself ( one of brother ) residing far away from where the land is sold so in this scenario I gave power of attorney for 1/6 share to my son in law, accidentally I have not signed the power of attorney despite this transaction take place , and my son in law signed the paper on behalf of me before receiving the full consideration , and total share of consideration have not received and now buyer has full possession of the property, can we make total sale deed wrong or void or contract can be total cancelled on behalf that power of attorney is not duly signed and whatever money received from buyer by attorney we are giving back to buyer , can we cancelled total agreement and under income tax act section 269ss suggest that cash transaction over 2 lakh are not allowed can we on this basis we make total agreement wrong and this is not registered property deal in govt