Nri can buy agricultural land in karntaka

If any agricultural land is existing in your brother name and your name you may buy  agricultural land in Karnataka with out any hurdles, as per Karnataka Land Revenue Act  and Rules. With regard to your investment it is different matter subject to NRI and FERA Rules. 

yours 

R.S.K.Singh

Thank you for the reply;

I have ancestor land in my name, but now i am NRI, so can brother or mother can buy land with my money ?

RBI i says this

Can an individual resident Indian borrow money from his close relatives outside India?

Yes, an individual resident Indian can borrow sum not exceeding USD 250,000 or its equivalent from his close relatives³ staying outside India, subject to the conditions that:

1. the minimum maturity period of the loan is one year;
2. the loan is free of interest; and
3. the amount of loan is received by inward remittance in free foreign exchange through normal banking channels or by debit to the NRE/FCNR(B) account of the NRI.

https://www.rbi.org.in/scriptts/FAQView.aspx?Id=52 

can they use this money to buy land ?

If you are citizen of India it is sufficient to buy property in India. Regarding your investment the above rule is applicable. 

Yours

R.S.K.Singh