Can Father of Minor in whose name the property is make GPA

I have purchased a property through a registered sale deed from a person who got the property from another person (Z) who got the property (1.1gunta) registered from a GPA holder (Y). Y got the GPA from the father of a minor (X)(age 14 years at that time) in whose (minor) name the property was existing (beyond that no documents). The GPA is registered and layout is formed (each site 1.1 gunta). The said property I purchased is A khata as called in Bangalore. It has all the betterment charges paid and comes within BBMP limits of Bangalore. The GPA is done in 1979. Now for the construction of the said property (3'0 X 40') when I approached a bank for loan, the legal consultant of the Bank has said that since the property was in the name of the minor (X), he can claim the possession any time as the court permission is not taken at the time of GPA. Hence legally not tenable to give loan. But some advocates told me that the minor can claim the property only upto 3 year of becoming major. Now it is 33-34 years passed after him becoming a major. Also he is no more. Can his children claim the property. How do I convince the legal consultant (like any judgements of similar cases) to help me get the loan.