Even in the ramayana it was written as agastybhratha ( sri rama goes to his asrama before going to agastya\'s asrama). the sage agastya was so famous that even his brother was known as agatya-bhratha ( brother of agastya). if you know his real name kindly share it with us after giving sufficient time for the other forum friends to answer.
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Sage Agasthya was the son of Pulasthya and Havirbhoo(d/o.sage kardama and Devahoothi). agasthya yad 3 brothers 1. sage Vasishta 2. sage Vishwavara 3.. sage Nidagha. as everyone knows that sage vishwavara was the father of Ravan