What would be the Right to Property owned by parents but the title was transferred to a married brother

hello po. Pls help. We have a house and lot bought by my eldest brother, the breadwinner of the family and single at that time. The property was in the name of our parents. Later, my mother, after my father died pawned our lot. When she can't pay the loan she sought the help of my eldest brother who is married already, to pay the loan in the amount of P30K. My eldest brother wanted to ensure that the property would not be pawned again, so he told us he will transfer the title of the property to his name. At first, my other brothers and sisters don't like the idea because me (single) and my mother were living in that house, my sisters and brothers with their families have their house built in that lot, and we are not sure what will happen in the future but because of love and respect to both my mother and eldest brother, with heavy heart we agreed. As years went by, I always heard my mother asking my eldest brother to write a document stating that the transfer of the title of the property is just a mere condition so it could not be pawned or a document that will says that only the lot will be pawned to him, except the house. It was 14 years now when my mother died and second death anniversary of my eldest brother but the request of my mother did not materialized. We still live in that property but My problem is this: the widow of my eldest brother pawned the property at P500K with 5% monthly interest. She said she needs large amounts of money because she had to pay dividends and return the investments of her investors. I have doubts with the intentions of my sister-in-law because I already talked with her never pawn the property since they have other properties she can use to pay her investors. She and my brother had only only adopted child. A child of her own relative. Please advise on whatever capacity, rights or our family will do to secure our property. Thanks a lot.