loan and house title (need advice)

Good day,

i would like to ask for an advice regarding my wife's family situation.
here is the details:
The grand parents of my wife owns a house that is titled to them. They borrow money from a specific neighbor. the grandparent borrow regularly so what the lender did is make a written aggreement with regards the loan. from 1970's till early 2000's they borrow around 100k to 200k. unforutnantely both grandparents died due to old age. so basically the house is inherited by the son and daughter of the grandparents(my mother-in-law and his brother). one day the lender pay for the amiliar for the house and my stupid mother in law allowed the lender to mark the title because the grandparents owe the lender. i ask my wife to talk to the lender to ask how much is the loan and we will pay for it in a monthly basis. but the lender computed the loan with a whooping 1.5M because of the interest.

is there something we can do about it? can we file something so that we can pay her and remove the marking in the title?
please do give me advice what to do to resolve the debt of my wife's family.

TIA

-Paolo

please help