PNR owned lot. Family fighting over house on PNR lot!

Hi my grandmother had a dilapidated wooden house on a PNR lot, My parents tore down the dilapidated house and built a big 3 floor house on the same PNR lot, the new house was built after my grandmother had passed away.  which my parents let my cousins live in as care takers until they get married or have a family that they have to move out, my parents let my cousins stay even though they got married and had kids. My cousins also sold all and anything with monetary value over the years my parents sent from the USA. My cousins also received monthly allowances from my parents. Now we are trying to evict them and file for "Recovery of Possession'' through the court. My cousins came up with a "Quit claim" document that had supposedly have my grandmothers thumb print giving half of the old dilapidated house to them which in turn they say that they own half of the new house my parents built ( old house value p8,500, new house value p1,780,000). My question is that the Quit Claim only has my grandmother finger print which no one knows if its truly hers or just anyone's finger print and one witness with no attached affidavit that the witness is a disinterested party , My aunt and uncle who were suppose to receive the said property who lives in the house with no job and stayed at home all day did not even have their signature as witnesses. I have attached the document for everyone to see. My 3 cousins also attacked me on Christmas day 12/25/13 and they filed charges against me but all the witnesses only saw them being the aggressor who assaulted me.  My questions are;

1) How can I find out if the Quit Claim is real?
2) if it is real do my cousins have any right to the new house?
3) if they do have rights to the new house (worth p1,780,00)  
     are they entitled to get half of the new
    house (worth Old house p8,500)?
4) Should I file counter charges against my cousins?

QUIT CLAIM;