sangla ng lupa ng biyenan

Hello po! Requesting advice tungkol sa isinanglang lupa ng brother and sister in law. 2 Lots was owned as a "declaration" by my father in law. The borrowers claim that they are gradually paying the debt(has been 8yrs cycle. It was a cycle to them to borrow again the money they paid for... in other words, hindi po natutubos yung declaration na 2 lupa. Until my brother in law died (seaman). He received lumpsum amount of P3M from insurance. We were hoping Sister in law will pay for the debt, because the family properties were at stake. and we trust her. Until time came, we knew that she owed huge amounts to other lenders too. She left the family and the house. She opened up a business (as she claims) and rents house fo 6000. She paid other lenders amount totaling to 1.5M. And the rest, we do not know where it went. She claims, has only 200,000left. Stil she disregards her payments pertaining to family properties, has ben 8yrs and yet did not prioritize closing the debt. Father lend her these declarations (not titles yet)about 8ys ago, until now was not given back. Wala pong pinirmahan ang tatay na katunayan sa pagkakasangla ng lupa nya. Yung 1 lupa, nakatirik yung bahay ng borrower, and the rest belongs to 3 other siblings. Verbal po na sinabi ng tatay na pamana ito sa mga anak, ngunit hanggang ngayon, ang lupa ay hindi pa nahahati so it is counted as 1 property. Nagverbal po yung borower na balak nya ibenta na yung share nya (with no written proof/documanetation na kanyang pagaari yung share nya). Hiling lang po ng family na tubusin nya yung 2 properties kc mawawalan ng tirahan ang occupants ng properties na ito. Seems like hindi sya willing magbayad or tumubos. Maari po ba siyang sampahan ng kaso or ilapit sa korte? What is the legal way to handle this?Please advise us.