Poa of demised nri from malaysia

My brother was a citizen of Malaysia, he passed away in 2017. He has some properties in India. Can my sister-in-law and the 5 children give a POA to the eldest son-in-law who is an Indian citizen who is a PR of Malaysia to sell the properties on behalf of the family. Can the POA be attested by a Notary Public and adjudicated in Tamil Nadu. What is the duration for adjudication and the validity of the POA. We would appreciate for an answer as we would like to come to India in the month of June 2018. Please advice the procedure. Tq