Am curious to know about the history of SriVaishnavism and the tridandi monks before Sri Ramanuja.
All Sri Vasihnavas, Vadakalaias and Thenakalais, trace their acharya lineage through the Acharya who initiated them into Sri Vaishnavam. This initiation ritual is called Samasrayanam. All these lines of acharayas finally leads to Bhagavat Ramanuja. As you trace further up, you ultimately end up with Sriman Narayana.
The earliest of uninterrupted line of Acharyas is Sriman Nathamuni. After N, according to the Sri Vasihnava Sampradaya, the lineage jumps to Nammazhvar, aka Shatakopan. Then, the lineage moves celestial to Visvaksenar, aka, சேனை முதலியார் (leader of the congregation of Nithyasoorees and Mukthas), and Sri (Thayar), and on to Sriman Narayana.
If I understand HH correctly, she is interested in the Acharyas between Ramanuja and Nathamunigal. What follows is based on the earliest of the Sri vaishnava hagiographies called ஆராயிரப்படி குருபரம்பர வைபவம் by பின்பழகிய பெருமாள் ஜீயர்.
What is now understood as Sri Vaishnavam was established by Sriman Nathamunigal (N). The legend of N says he came across a group of travelers from Kumbakonam who were singing just 10 verses from Swami Nammazhvar's Thiruvaymozi, in the temple in Kattu Mannarkovil, near Chidambaram and the birth place of the great Dalit leader and Congressman late Ilaiaparumal.
These ten verses are among the most beautiful and moving of the more than 1000 verses of Thiruvaymozhi. Here is the first of these 10 and you see for yourself.
ஆரா அமுதே அடியேன் உடலம் நின்பால் அன்பாயே
நீராய் அலைந்து கரைய, உருக்குகின்ற நெடுமாலே
சீரார் செந்நெல் கவரி வீசும், செழுநீர்த் திருக்குடந்தை
ஏரார் கோலம் திகழக் கிடந்தாய், கண்டேன் எம்மானே
These 10 pasurmas are packed with so much devotional love, it indeed melts (உருக்குகின்ற நெடுமாலே) the heart of even a heathen like me. Please permit me to cite just a few more phrases from these 10 pasurams.
உன்னால் அல்லால் யாவராலும் ஒன்றும் குறை வேண்டேன்
தரியேன் இனி, உன் சரணம் தந்து, என் சன்மம் களையாயே
யாழினிசையே அமுதே, அறிவின் பயனே அரியேறே
N was so taken by these 10 verses he spent the rest of his life gathering all the Azhvar pasurams. He is credited with not only bringing out Nammazhvar poems, but all the twelve Azhvars as well. But for him, we would not have the 4000 Dhivya Prabhandham. He set the verses to music and dance. The choreographed rendition of the Dhivya Prabhandam is called Arayar Sevai and is conducted every year in many temples.
N had a grandson named Yamuna. He saw a great deal of devotional potential in young Yamuna. But N passed away before he could have chance to mold him. But, in his deathbed, he made his sishya Uyyakkondar who became the next Acharya, promise that he will take the responsibility for guiding Yamuna.
Not a whole lot is known about Uyyakkondar. He also passed away and the responsibility of guiding Yamnua fell to the next Acharya Manakkal nambi.
In the meantime, Yamnua had amassed great wealth thanks to his vast Vedic knowledge and brilliant debating skills. He acquired the title Alavandhar, and was a king of a small kingdom. He was immersed deeply into his political life and had no time for anything spiritual.
Somehow, Swami Manakkal Nambi gained Alavandhar's trust and guided him away from his lowkeeka life into Vaideeka life. After Swami Manakkal Nambi, Alavandhar became the acharya. The story of Alavandhar is quite interesting, but I will skip it for fear of too great a digression.
As far as I can tell from the text, Swami Alavandhar was the first Sanyasee in the Acharya lineage. Among his works the one that stands out is Sthothra rathna in Samskritham. The verses of this poem indeed deserve every syllable of the title Sthothra Rathnam. It is indeed a Rathnam surpassed in brilliance by no other. It is upon hearing this poem Bhagavat Ramanuja finally abandoned his old associations and became a complete Sri Vaishnava. By this time he was already a Sanyasee and Alavandhar was already dead.
Swami Alavandhar had an eclectic group of sishyas that included Swami Thirukkachchi Nambi, a vaishya, and Swami Maraner Nambi, a dalit. Other sishyas of Alavandhar who later became teachers for Ramanuja were, Ramnuja's own uncle Periya Thirunmalai Nambi, Thirukkoshtiyur Nambi, Thirumalai Andan, and Thiruvaranga Perumal Araiyar. Of these Thirukkoshtiyur Nambi is perhaps the most prominent. However, it is Swami Periya Nambi who is in the lineage of Acharyas between Alavandhar and Ramanuja because it was he who initiated Ramanuja into Sri Vaishnavam at the Ramar temple in Mathurandhakam. As far as we can tell Swami Periya Nambi was a grahastha.
So the earliest of Thridhandees of the order were Alavandhar and Ramanuja. There is lot of significance for threesomes in Sri vaishnavam. There is the three thathvas, Chetana, Achethana, and Iswara. There is the three gunas that must be bound and kept in control. There are three types of Jeevas, namely, Baddas, Mukthas, and Nithyasoorees. There are three types achetanas, namely, thraiguNya matter, Sudda Satvam of Sri vaikuntam, and Kalam.
Of all these, it is the three thathvas that represent thridhandams.
I invite others to add if I have missed anything.
Cheers!