The brother of Tāmasa Manu was the fifth Manu, named Raivata. His sons were headed by Arjuna, Bali and Vindhya.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
पञ्चमो रैवतो नाम मनुस्तामससोदरः । बलिविन्ध्यादयस्तस्य सुता अर्जुनपूर्वकाः
pañcamo raivato nāma manustāmasasodaraḥ | balivindhyādayastasya sutā arjunapūrvakāḥ
SB 8.5.2