Gift tax

Hi I am living in USA. My wife's sister and her husband has bought some property last year. Now they are in need of showing their income, but as per their tax filing last year, they didn't mention sufficient income. Hence, they are asking me to help them by giving them a gift letter that I gave some 30 lakhs, with which they want to project as they have bought the property with that money. Last year I have bought some plot in India, and I have drawn some cash. As the market value is more than the Government rate, I have to spend more money. example - I bought the plot with x lakhs which is market value. The Govt. rate is y lakhs. Now the difference of market value vs Govt value is 30 lakhs. i.e - x-y= 30 lakhs. Now a Chartered Accountant from Wife's sister family asked me if I can give them a letter that I gave them 30 lakhs as a gift for buying their property. Now I am not sure if I can do that. If I do it, will I get any issues from Income Tax department. Do I need to pay the Gift tax. Incase if there is an audit, do I get any problems. Please reply me with the above details. Thanks Rajashekhar S