(Srila A.C. Bhaktivedanta Swami Prabhupada. Sri Chaitanya Charitamrita Adi-lila 10:106 purport.)
Visvarupa was the elder brother of Gaurahari, Lord Sri Caitanya Mahaprabhu. When arrangements were being made for the marriage of Visvarupa, He took sannyasa and left home. He took the sannyasa name of Sankararanya. In 1431 Sakabda Era (A.D. 1509), He disappeared in Pandarapura, in the district of Sholapur. As an incarnation of Sankarshana, He is both the ingredient and immediate cause of the creation of this material world. He is nondifferent from Sri Caitanya Mahaprabhu, for the amsa and the amsi, or the part and the whole, are not different. As an incarnation of Sankarshana, Visvarupa belongs to the quadruple manifestation of catur-vyuha. In the Gaura-candrodaya it is said that Visvarupa, after His so-called demise, remained mixed within Sri Nityananda Prabhu.
(Srila A.C. Bhaktivedanta Swami Prabhupada. Sri Chaitanya Charitamrita Adi-lila 13:74 purport.)
Because Maha-sankarshana is the ingredient and efficient cause of the cosmic manifestation, He is present in every detail of it. Lord Caitanya therefore called Him His elder brother. The two brothers are known as Krishna and Balarama in the spiritual world, but at the present moment they are Caitanya and Nitai. Therefore the conclusion is that Nityananda Prabhu is the original Sankarshana, Baladeva.
(Srila A.C. Bhaktivedanta Swami Prabhupada. Sri Chaitanya Charitamrita Adi-lila 13:78 text and translation.)
"My elder brother, Visvarupa, has taken sannyasa and gone to South India. Now I must go search for Him." (44)
"Please permit Me to go, for I must tour South India. With your permission, I shall soon return very happily." (45)
Upon hearing this, Sarvabhauma Bhattacarya became very much agitated. Catching hold of the lotus feet of Caitanya Mahaprabhu, he gave this sorrowful reply. (46)
Accompanied by His personal associates and Sarvabhauma Bhattacarya, Sri Caitanya Mahaprabhu circumambulated the altar of Jagannatha. The Lord then departed on His South Indian tour. (58)