Complex sentence: Atulprasad was raised by his maternal grandfather, a renowned Brahmo social reformer Kalinarayan Gupta, who initiated him in music and devotional songs.
Split into simpler sentences: Atulprasad was raised by his maternal grandfather Kalinarayan Gupta, who was a renowned Brahmo social reformer. It was Kalinarayan who initiated Atulprasad in music and devotional songs.