Status of agpa with possessesion

A is the owner of a property and executed a registered irrecoverable AGPA with Possession with consideration in favour of X. Later X expired and without intimating A being the original Owner of the property the family members of X by submitting fraudulent and fabricated documents got that property transferred to several persons. In one OS they mentioned another property for succession certificate / legal heir. Court specifically mentioned that for succession they should go for a Declaration Suit. By submitting this order they sold the property. Now the question is whether Mr A's signature also required for sale Deeds or the AGPA will stands cancelled ? Please provide me your valuable and experienced views.