Irresponsible grandson trying to take over property how to stop him

my uncle wrote a regestered will to his(late) daugter's son.he did not revoke it and wrote his next will on a white paper in favour of his wife.the grandson did not look after the grandparents in ill health.they suffered a lot.now he died and the second un-regestered will is in the house. the wife enqiried the witnessess for clarity and they replied it as true.the grand son is now ready to trasfer the agri-proprty to his name.this grandson only retured to them after this testater's death.till now he didnot take the interest of his grandmother too.can the regestered will be challenged.do the unregestered will has power than registered will.the widow is willing to transfer her husband's property to her name.the title deeds and adhaar cards of both the gransdparents are missing.these are stollen by the grand son after her husbands death as per the widows words.what can we do for this old lady who is ill due to heart valve problems??