This section is from the book "Some Contributions Of South India To Indian Culture", by S. Krishnaswami Aiyangar. Also available from Amazon: Some Contributions of South India to Indian Culture.
It was already pointed out that practically all the sixty-three devotees must have lived in the period which for convenience may be called the age of the Pallavas, taking it in the broadest sense as extending from about A.D. 200 to 900. It was also pointed out that the earliest of them may reach back to quite the commencement of the age of the Pallavas and the latest of them cannot have been many generations after the practical abolition of the Pallava power in South India. The Chola Ko-Chengan and the hunter Kannappa, and some others among these are referable to the early period of the age of the Pallavas. Sambandar, Appar and a certain number of others are referable, on what might be regarded certain evidence, to the seventh century A.D. Of these, Sambandar had a comparatively short life while Appar must have lived a man of ripe old age. The two are however generally referred together, and the younger is generally regarded as the more influential of the two, both in regard to his following and the importance of his teaching. Then follows the third section headed by Sundaramurti. He had a friend in another of the sixty-three, a Seraman Perumal. These had been referred, the one as providing the occasion for the founding of the Kollam era and the other as having celebrated in a poem the other sixty-two devotees, to the early part of the ninth century A.D. Of these, Sambandar, Appar and Sundaramurti constitute the three recognised leaders of the school of bhakti as represented by the sixty-three Adiyars or Nayanmars, and the works of the three constitute the first seven sections of the Saiva literature of this school. The oldest among these Appar was born a Saiva, became a convert to Jainism and leader of the Jain settlement at Patali (now the new town of Cuddalore) and became a Saiva again as the result of a miracle, by means of which Siva cured him of what seemed an incurable disease. Saiva tradition has it that it was through his influence that the Pallava King Mahendra Varman was converted to Saivism from Jainism. There is a burlesque" Malta Vilasa Prahasana " ascribed to this Pallava Mahendra Varman where he brings into a somewhat ludicrous colloquy a Pasupata, a Kapalika and his wife, and a Bauddha, and no Jain however is brought into this religious squabble. This may support the contention that he was a Jain to begin with. His monuments however seem alike devoted to the Brahmanical trinity though this is no bar to his having been a Saiva.
According to the story as embodied in the Periyapuranam of the life of Sambandar the Pandya contemporary had adopted the faith of the Jains while his wife, a Chola Princess was a devoted Saiva. So also was his chief minister. Through the influence of these latter two, Sambandar obtained the opportunity to convert this Pandya to Saivism. Both the queen and the minister are counted among the sixty-three canonical devotees. The miracle that brought about the conversion of the king was that after a successful disputation with the Jainas, Sambandar made the hunch-backed king stand erect and gave him the name "Ninrasir Nedumarar" which can be interpreted the great Pandya of enduring prosperity, or the great Pandya who had stood erect. It is on this occasion that at the instigation of Sambandar the whole body of Jains in Madura are said to have been impaled. This story of persecution has in it features which seem the common features of similar stories. Such stories are told of a Jain king of Kanchi who gave to Buddhists similar treatment, and of the Vaishnava apostle Bama-nuja having treated the Jainas similarly by instigating the Hoysala king Vishnu Vardhana against them. In such cases these stories seem to have been concocted by the later hagiologists to enhance the glories of their own particular form of religion. In each one of these cases it can be proved conclusively that there is no evidence of a general act of persecution, such as is described, as these religions flourished in undiminished influence even after the period to which these persecutions are ascribed.