Raen is a Tinker and the leader (Mahdi) of his group. He is married to Ila and the grandfather of Aram. He first met Perrin and Egwene when they got separated from the rest of the group in Andor. He is the one who explained the Way of the Leaf to the two of them and also about the search for the lost songs of the Tinkers.
For more details on Raen, visit Encyclopaedia WoT.