Translated from Yatindra Pravana Prabhavam
Ramanuja was born north of Srirangam, in Sriperumbudur, to spread the Srivaishnava sampradhayam in both Sanskrit and in Tamil. Through his birth "nArANanaik kAttiya vEdham kaLipputradhu", "thenkurugai vaLlal vAttamilA vaNthamizh maRai vAzhndhathu". Manavala Mamunigal was born south of Srirangam, in Azhvar Thirunagari ("aranga nagarum mEvu thirunagariyum vAzhavandha maNavALa mAmuni"), in order to spread the sampradhayam in Tamil alone. Even though, Mamunigal is well versed in both languages, one is stressed to show his greater interest in it.
Periya Jeeyar left his janma bhUmi of Azhvar Thirunagari and came to Srirangam, saw Lord Ranganatha in the middle of the Kaveri, lived with SriVaishnavaSri, and continued to develop SriRangaSri, the Sanskrit Vedas and the Dravida Veda.
Ramanuja brought out the meaning that Sriman Narayana is the Lord of all ("ellA uyirkatkum nAthan arangan"). Mamunigal brought out the meaning that Ramanuja is the saviour for all ("palluyirkkum viNNinthalai ninRu vIdaLippAn anaiththulagum vAzhappiRandha ethirAsa mAmunivan").
Ramanuja's vaibhavam was subdued until Mamunigal's birth. Mamunigal is the lamp that brought the light to Ethiraja's vaibhavam.
Their avataram is similar to that of Nara Narayana. Just as Narayana came as both acharya and sishya, so too Adisesha came as acharya and sishya.
Ramanuja brought out the greatness of Narayana ('nArAyaNa vaibhava prakAsha') while Mamunigal brought out the greatness of Ramanuja ('rAmAnuja vaibhava prakAsha').
Both the namas Narayana and Ramanuja are made of four aksharas. Since Mamunigal is the leader of those who follow the fourth path, he follows the charama 4 akshara name which is Ramanuja.
Even though Madhurakavi is the direct disciple of Azhvar, the final thiruvadi of Azhvar is Ramanuja (Azhvar's padhukas are known as Ramanujan). Similarly, even though disciples such as Kooraththazhvan and Mudhaliandan are close to Ramanuja, Yatindra's final thiruvadi is Yatindra Pravana.