Valmiki Ramayana Bala Kanda Sarga 20 Shloka 17
Original Shlokaश्रूयते हि महावीर्यो रावणो राक्षसाधिप:।।1.20.17।। साक्षाद्वैश्रवणभ्राता पुत्रो विश्रवसो मुने:।
1 source checked for this shloka
साक्षात् evidently, वैश्रवणभ्राता brother of Kubera, विश्रवस:मुने: ascetic Visrava's, पुत्र: son, राक्षसाधिप: king of rakshasas, रावण: Ravana, महावीर्य: of great prowess, श्रूयते it is heard.
Ravana, king of rakshasas, is the brother of Kubera and son of ascetic Visravana. He is said to possess great prowess.