Valen was born Jeffrey David Sinclair (May 3rd 2218 on Mars). He is the one of 200 survivors that took part in the Battle of the Line - the final assault of the Minbari against Earth. After the Minbari captured him and took him aboard their Grey Council ship the Minbari surrendered suddenly. Only few know why. Some members of the Grey Council believed that he was one of the mysterious race Valen told them they'd need to ally with in the impending fight against the darkness. Fewer of them believed that he was Valen himself, the 'Minbari not born of Minbari'.

Sinclair was the first Commander of Babylon 5 until he was reassigned to Minbar just after Christmas of 2259 as their first Human ambassador. Whilst he was there he became Entil'zha and Leader of the Rangers.

Towards the end of 2260 he took some of the command crew from Babylon 5, and they aided him in returning Babylon 4 to the past, to use as a base of operations in the last Great War. He left with the station (and Zathras) and subsequently became Valen with the use of the Triluminary/Chrysalis.

As Valen, he led the Minbari - alongside the Vorlons and some First Ones - into battle against the 'ancient enemy'. He taught them many things, including how to live, how to die and how to respect each other. He set up the Anla'shok and the Grey Council and treated all the castes with the same respect.