Inherited property

Hi, From the property of grand father 2 shares were made one for my dad and his eldest brother and documented it 3 decades back, my father got the least as he choose to settle the division process smoothly.My father doesnt have the division document as he trusted his brothers and now my cousins misguide giving wrong extent of few plots(less than what was mentioned) in whatever share we got in different locations. I want to settle this amicably but my cousins talk about verbal agreements happened between my dad and his brothers in the past and create confusion in our share. I understand that we should refer the division document which is my aunts possession and shes doesnt give. in the mean while my dads brother sold few assets(after division) out of their share but wrote a wrong extent(increased) in few registration documents(sold to other parties). Things are very complicated now.My dads late eldest brothers children are dividing their assets now and they might include our assets as well in their division, what should i do to avoid that? 1. how can i get all the sale deeds made out of my grand fathers assets( before and after the division)? can i get the division documents(between my dad and his brothers) ? If that document is not registered i believe i can never get it. In that case what legal options do i have? 3.Before filing a case can i send a notice or something just to get them on track as i believe they wouldnt fight a case as they ( my dads late brother)are at fault and it can be proved in the court ? if i send a notice should i also include the parties who have bought the plots from my dads late brother(after or before division? 4. There are few of my grand fathers assets where my dads late elder brother sold the property without my dads consent or sign before the division , can i claim those now? if i win the case now who will be at loss my cousins or the person who bought it? 5.If they come to my terms then what documentation should i make to make sure my assests are secure in future? 6.Should i send notices to all the legal heirs in case if i have choose to do so? 7.My dad bought a peice of land from his brother and it was a gift deed on my mother, if i choose to send notices will this plot get into a problem? 8.My dads brother mentioned less extent in a gift deed executed on my moms name, the remaining 300sft of land of his share is still lying there, if he agress to correct the gift deed what is the procedure?? My intention is to retain and enjoy the assets which my father has righfully inherited in a peaceful manner, i donot wish to fight a court case . Please help me understand my options.