GPA to registration

hi, This is about a house that my grandfather bought in the year 1985, at that time the original seller had executed a GPA in my grandfather's name. After that my grandfather executed the GPA in my Mothers and Fathers name in the year 1993. Both the original seller and my grandfather have passed away. We are now planning to register the property in my name. What would be the procedure and legally correct way of going about this. What documents would we require. The original seller has children who might / might not be aware of this. And my mother has her brothers and sister who have no issues with registration. Also to clarify we are not trying to usurp anyone else's property we are staying in this place since 1985. The GPA between the original seller and my grandfather states that the children of the original seller have no stake or claim on this property. Plz advice. We are a muslim family so is it possible to get a HIBA on this property rather than registering it. Does HIBA hold the same value as the registering a property. Plz advice. Thanks in advance