Suit filed by care taker for stay on sale of property and money

A property purchased out of staff home loan from sbi where I worked was given by us for stay in Lucknow in 2004 to my father-in-law and mother-in-law out of regard and love and affection as they were having quarrels everyday with their son and daughter-in-law with whom they stayed. It was a clear understanding though not written that they will vacate the house in case I needed to sell it. However, when I actually needed to sell it in 2015 my father-in-law filed a case against me and my wife that is, his real daughter and son-in-law asking the court to grant a stay on sale. He also claimed in the plaint that he had rendered some monetary help, out of love and affection, in the purchase of the said property and therefore, he is entitled to have a part of the property or value thereof. Property is in my and my wife's joint name and was mortgaged to sbi to secure the staff home loan. The case has been languishing for the last 3 years and even evidence stage has not been completed due to several adjournments granted to the plaintiff on the grounds of old age (88 years approx.) and sickness. Actually he is keeping good health considering his age, he himself is drawing pension of 20000 per month from sbi and has two sons well established and having their own properties and regular income in Lucknow itself. It's a clear case of blackmail and extortion using the legal machinery in connivance with his sons. He is also trying to implicate me in a false criminal case and has approached cjm court in lucknow under cpc section 156(3). How do I deal with the matter effectively to see that it ends at the earliest without any harm to me or my wife? I have retired from sbi in 2017 and settled in Pune.