Investment on dad's name

Hi there, I have transferred some USD in the year of 2007 and money was invested (not right away) in the property in India by my dad. Since I was in US, my dad invested on his name. My dad-mom visited US in 2016 and unfortunately my dad did not survive after one month of treatment in US. Me and my husband took care of all expenses of his hospitalization and treatment. After dad's demise, I requested my family (mom and both brothers) to get my returns from the invested property by transferring property on my name. My mom and both are brothers have started replying as if they are not aware of any money given to my dad. After some extended family involvement, now they are ready to return the same amount what was given in 2007 in terms of rupees (not USD) with only 5% interest rate although my investment has appreciated 10 times. The exchange rate of USD vs INR in 2007 vs 2021 has a huge difference and when I did not gave to put in the bank...plus current interest rate in bank is too low. What should I do in order to get my hard earned money with best of my interest.