Swami Brahmananda was born on 21st January 1863
One day Sri Ramakrishna fervently prayed to the Divine Mother: “Mother, it is my desire that a boy with sincere love for God should always remain with me. Give me such a boy.” A few days later, sitting under the banyan tree at Dakshineshwar, he had a vision of a boy. Sri Ramakrishna had a second vision: “Just a few days before Rakhal’s coming I saw Mother putting a child into my lap and saying, ‘This is your son.’ I shuddered at the thought and asked her in surprise, ‘What do you mean? I too have a son?’ Then She explained with a smile that it would be a spiritual child, and I was comforted. Shortly after this vision Rakhal came, and I at once recognized him as the boy presented by the Divine Mother.”
(p.75, God Lived With Them)