He was the successor of Hazrat Umar Ibn Al-Khattab (radi Allahu anhu). He was related to Prophet (pbuh) through his mother and to Abu Sufyan Ibn Al Harb through his father.
How much did he know the Prophet (pbuh)?
Even before accepting Islam he used to know Prophet (pbuh) as As-Saadiq Al-Ameen which means the truthful the trustworthy.
What is special about him?
He got the nick name Dhun-Norain means possessor of two lights. He was distinguished in marrying two daughters of Prophet SAW.