Valmiki Ramayana Yuddha Kanda Sarga 30 Shloka 21

आन्य another, गद्गदस्यैव Gadgada's, पुत्त्र son, शतक्रतो an epithet of Indra, (known as Dhumra), गुरुपुत्र son of Brhaspati, (Kesari), यस्य his, पुत्रेण by his son Hanuman, एकेन alone, रक्षसाम् Rakshasas, कदनम् killing of many, कृतम् did.

Another son of Gadgada is Dhumra. One who killed many Rakshasas is Hanuman, the son of Kesari, who is the son of Brhaspati.