During one Kalpa (a day of Brahma), there lived a handsome Gandharva with a melodious voice. Once he was in an inebriated state and entered the assembly of Devas who were performing rituals. Instead of singing glories of God he sang amorous songs detailing the beauty of celestial women and lovemaking.
The angry Devas cursed him to be born on earth. This was at the fag end of a Kalpa and it was Kali Yuga on earth.
On earth, he was born in the house of a servant. When the boy was five years old, a group of saints came to his town. He got the opportunity to be with them. This close association with the sages at the young age developed in him devotion for God.
From that day, he roamed around singing the glories of God. Later he sat in meditation and did intense penance. Pleased with his devotion, Lord Vishnu blessed him that in the next cycle of creation, or kalpa, he will be born as the son of Brahma.
Thus in the present Kalpa, Sage Narada was born as the son of Brahma. He roams around the world singing the glories of Narayana.