Yamunacharya, Nathamunigal's grandson, was born at Veeranarayanapuram and was a brilliant student even as a boy. According to tradition, when he was about twelve, a proud court scholar named Akki Azhwan was demanding tribute from every scholar in the land. Young Yamunacharya took up his challenge and defeated him in debate before the king. The queen was so delighted that she called him Alavandar, "the one who came to rule", and the king gave him a share of the kingdom.
For some years Alavandar lived as a king, until Manakkal Nambi brought him back to the Lord and showed him Sri Ranganatha at Srirangam. He gave up his throne, settled at Srirangam and became the leader of the Sri Vaishnavas. His works — Stotra Ratnam, Siddhi Trayam, Agama Pramanyam, Gita Artha Sangraham and Chatusloki — laid the ground on which Sri Ramanuja would build.
According to tradition, on a visit to Kanchi Alavandar saw the young Ramanuja walking among Yadavaprakasa's students, and prayed to Lord Varadaraja that this young man would become the leader of the sampradaya. He prepared five of his disciples — Periya Nambi, Thirukkoshtiyur Nambi, Periya Thirumalai Nambi, Thirumalai Andan and Alwar Thiruvarangapperumal Arayar — to pass his teaching on to him.
When his end drew near, Alavandar sent Periya Nambi to bring Ramanuja. By the time they reached Srirangam he had already left this world, and three fingers of his hand stayed folded. Ramanuja understood that these were three unfulfilled wishes and vowed before everyone to fulfil them — among them, to write a commentary on the Brahma Sutras. As he made each vow, a finger opened.