Śīghraga was Agnivarņa’s, and Maru was Śīghraga's son. And Maru's son was Prasuśruka, and from Praśuśruka sprung Ambarīşa.
शीघ्रगस्त्वग्निवर्णस्य शीघ्रगस्य मरुः सुतः। मरोः प्रशुश्रुकस्त्वासीदम्बरीषः प्रशुश्रुकात्॥