Sri Caitanya Mahaprabhu was born in Navadwipa in 1486 as the son of Jagannatha Misra and mother Saci, while Srila Nityananda Prabhu was born in Ekachakra in 1474, as the son of Hadai Pandita, and Padmavati. They grew up separately and met only much later, already in adult life. However, Lord Nityananda and Sri Caitanya Mahaprabhu are considered brothers, how is it so?
The first reason is that Sri Caitanya Mahaprabhu is Krsna Himself, and Lord Nityananda is Balarama. In this way, they are eternally brothers, and the relationship doesn’t change when they come to perform their pastimes in this material world.
There is however another reason that is a little more esoteric.
Sri Caitanya Mahaprabhu had an older brother called Visvarupa. He was very fond of Him, but Visvarupa took Sannyasa in 1491 from Krsna Bharati in Varanasi (at the time Lord Caitanya was just 5 years old) when his parents tried to arrange his marriage.
After taking sannyasa, Visvarupa traveled through the holy places and disappeared in Pāṇḍarapura under mysterious circumstances.
On his purport to CC Madhya 9.300, Srila Prabhupada mentions: “Śrī Caitanya Mahāprabhu’s elder brother was named Viśvarūpa. He left home before Śrī Caitanya Mahāprabhu and accepted the sannyāsa order under the name of Śaṅkarāraṇya Svāmī. He traveled all over the country and finally went to Pāṇḍarapura, where He passed away after attaining perfection. In other words, He entered the spiritual world after giving up His mortal body at Pāṇḍarapura. Śrī Raṅga Purī, a disciple of Śrī Mādhavendra Purī and Godbrother of Īśvara Purī, disclosed this important news to Śrī Caitanya Mahāprabhu.”
More details are given in the Sri Caitanya Bhagavata (Adi Khanda, Ch. 7): “Material happiness did not bring pleasure to Vishvarupa’s heart, where the bliss of Krishna-kirtana always stayed. When He was home, Vishvarupa stayed always in the room that was a Vishnu Temple. He hardly ever went to the other rooms. When His parents began to make plans for His marriage, Vishvarupa became very unhappy at heart. “I must renounce the world”, Vishvarupa decided in His heart. “I must go to the forest”, was the only thought in His heart. It kept Him awake at night. Only the Supreme Personality of Godhead can truly understand the desires that stay in the Supreme Personality of Godhead’s heart. After a few day Vishvarupa accepted sannyasa. In this world He was known by the name “Shankararanya”. The best of the Vaishnavas, He walked on the path that leads to the limitless Supreme Person. When saintly Vishvarupa left, the hearts of Sachi and Jagannatha Mishra burst into flames. The Lord and His parents loudly wept. Tormented by separation from His brother, Lord Chaitanya fell unconscious. I do not have the power to place in my mouth words that describe that torment of separation. Jagannatha Mishra’s home became filled with weeping. Seeing that Vishvarupa had accepted sannyasa, Advaita and the other Vaishnavas wept again and again.”
Sri Nityananda Prabhu appeared 12 years before Lord Caitanya. During these 12 years, he remained in Ekachakra and executed many sweet pastimes with his cowherd friends, being deeply loved by His parents.
Once, for example, he entered into the mood of Laksmana and re-enacted the pastimes with his friends. When hit by the puspa arrow He felt unconscious and no one could wake him up. All His friends, as well as His parents, started to cry bitterly until one of the boys remembered that in the pastime Hanuman brings medicinal herbs from Gandharva Hill. When the boy, playing as Hanuman, brought some herbs to Lord Nityananda’s nose, he regained consciousness.
Although He performed many of such wonderful pastimes, no one in Ekachakra could understand who He really was. In this way, He was able to remain incognito enjoying His childhood years.
He however did not stay in Ekachakra for very long. One day in 1486, shortly after the appearance of Sri Caitanya Mahaprabhu, a sannyasi visited the house of Hadai Pandit. Hadai Pandit was extremely anxious to receive this sannyasi in his house and get some of his association, but the mysterious sannyasi quickly said that he would stay only if he would be granted a request. Without hesitating, Hadai Pandit accepted the condition and thus the sannyasi stayed in his house for the night, accepting prasadam and lecturing on the Srimad Bhagavatam. Everyone was overjoyed.
The next day, however, the sannyasi revealed what his request was: He was set for a pilgrimage to all holy places and he needed a brahmacari assistant to travel with him. He thus requested Hadai Pandit to give him Nitai, his eldest son.
Both Hadai Pandit and his wife Padmavati could not tolerate even the idea of being separated from their son. However, he could not break his promise to the sadhu, and thus, with a very heavy heart he was forced to separate from his son. He instructed Nitai to be obedient to the sannyasi and assist him during the traveling. He explained to him how a great opportunity it was to visit the holy places with such a saintly person.
After this, Nitai traveled through the holy places and received the association of many exalted Vaishnavas, including Srila Madhavendra Puri. Later he received initiation from Shripad Laksmipati, the spiritual master of Srila Madhavendra Puri. The travelings of Sri Nityananda Prabhu ended only in 1506, when He finally met Sri Caitanya Mahaprabhu in Nadia, in the house of Nandan Acharya.
No one knows for sure who was this mysterious sannyasi. Some conclude that he was either a disciple of Shripad Laksmipati or a disciple of Srila Madhavendra Puri. Others however go further, concluding that he was nothing less than Visvarupa Himself, who took Srila Nityananda Prabhu in peregrination and later merged into Him.
While the dates don’t match (Lord Nityananda left Ekachakra in 1486, and Visvarupa took sannyasi only in 1491), we should keep in mind that pastimes do not always follow a chronological order and things often happen in a mysterious way. What we know for sure is that Visvarupa was an incarnation of Saṅkarṣaṇa and thus he was non-different from Srila Nityananda Prabhu. It could be that the mysterious sannyasi was an expansion of Visvarupa or someone empowered by him. In such a case, Vaisvarupa could have merged into Sri Nityananda Prabhu in this form. In any case, we understand that Visvarupa was no one else than a partial manifestation of Sri Nityananda Prabhu, and thus Sri Nityananda Prabhu is the brother of Sri Caitanya Mahaprabhu, as later understood by mother Saci.
In his purport on CC Adi 13.74, Srila Prabhupada mentions: “Viśvarūpa was the elder brother of Gaurahari, Lord Śrī Caitanya Mahāprabhu. When arrangements were being made for the marriage of Viśvarūpa, He took sannyāsa and left home. He took the sannyāsa name of Śaṅkarāraṇya. In 1431 Śakābda Era (A.D. 1509), He disappeared in Pāṇḍarapura, in the district of Sholapur. As an incarnation of Saṅkarṣaṇa, He is both the ingredient and immediate cause of the creation of this material world. He is nondifferent from Śrī Caitanya Mahāprabhu, for the aṁśa and the aṁśī, or the part and the whole, are not different. As an incarnation of Saṅkarṣaṇa, Viśvarūpa belongs to the quadruple manifestation of catur-vyūha. In the Gaura-candrodaya it is said that Viśvarūpa, after His so-called demise, remained mixed within Śrī Nityānanda Prabhu.”