"My father who was living in Jordan borrowed ( 15,000) from his brother in America in1987. At that time the 15,000 equaled JD4,500 Jordanian Dinars, and my father exchanged the dollars into Jordanian Dinar and used them. Now, 10 years later, he is able to return the money to his brother, but 15,000 equals about 10,000 Jordanian Dinars and not 4500. Does he have to return the money in the value of the dollar or in the value of the Jordanian Dinar?
Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. Your father has to give back 15,000 (fifteen thousand Dollars) to his brother as he had taken from him regardless of its equivalent to Jordanian Dinar at present or in the past, because the duty of a borrower is to pay back the same sum to lender. If your uncle agrees to a lesser amount with his pleasure, you father can accept it. And there is no problem in it. Allah knows best.
You can search for fatwa through many choices