Namaskaram, a small clarification, is Swami Alavandhar also the paternal grandfather of Sri Periya Thirumalai Nambi, apart from being his Acharyar.
Srimathe Ramanujaya Namaha,
Namaskaram ‘Adiyen’ Swami,
With Acharya ThiruvAdi Bhalam and Ammangaar Abhimaanam and Velukkudi Sri Krishnan Swami’s Aasirvadham, Adiyen has so far heard in Swami’s GuruParamparai upanyasam that Swami Alavandar (Yamunacharyar) had only fours sons while HE was ruling as a King before Swami Manakkal Nambhi corrected Alavandar and brought Alavandar back to SriRangam to crown as VishshitaAdvaita leader, which is when Alavandar took Sanyasam. However Alavandar’s Poorvashrama son’s also became Alavandar’s Shishyas later as:
1) ThiruAranga Perumal Arayar (who is one among the 5 Acharyas of Swami RamanujAr),
2) Sottai Nambhi (who was one among the 74 Simhasanapathis that Swami RamanujAr established),
3) Deivatthukkarasu Nambhi,
4) PillaiArasu Nambhi.
Periya Thirumalai Nambhi Swami was only a Shishya (disciple) of Swami Alavandar and didnot have any blood relationship with Swami Alavandar, but Periya Thirumalai Nambhi Swami was maternal uncle of Swami RamanujAr. Periya Thirumalai Nambhi Swamis sister Bhudevi (a.ka Smt. Kanthimathi) son was Swami RamanujAr.
Additionally so far, Adiyen or any other Ramanuja Dasas have not heard of any sort of blood relationship of Swami RamanujAr and Alavandar, hence we can conclude that Periya Thirumalai Nambhi didnot have any blood relationship with Alavandar except being a disciple.
The above is the MICRO answer.
But considering the SUBTLE form, the MACRO answer is that we can consider each of Acharyas or ourselves has blood relationship, since all of us are part and parcel of COMMON SUPREME ONE ALMIGHTY GOD SRIKRISHNA’s BLOOD.
Adiyen (ElayaAlwar) Srinivasa (DhoddayAcharyar) Dasan.