Hazrat Zubair (R) was the cousin of Rasulullah (Sallallahu Alaihi Wasallam). His mother, Safiyyah (Radiyallahu Anha), was the sister of the father of Rasuluallah (Sallallahu Alaihi Wasallam). He accepted Islam at the early age of 15 or 16. He is amongst the Asharah Mubasharah (the ten Sahabah who were given the glad tidings of entering Jannah). He participated in every battle with Rasulullah (Sallallahu Alaihi Wasallam) and was matyred in the Battle of Jamal in 36 A.H at the age of 60.
His full name is Khalid ibn Waleed Al Qurashi Al Makhzumi. His mother was Lubabah As Sughra, the sister of Hazrat Maymoonah (RA), one of the blessed wives of Rasulullah r, and the sister of the mother of Hazrat Abdullah ibn Abbas y. He was one of the nobles of the Quraish in the days of Jahiliyyah and accepted Islam after the Treaty of Hudaybiyyah in approximately 7 A.H.
Hazrat Amar ibnul Aas (R) - who was made commander of an expedition called Zaatus Salasil by Rasulullah (Sallallahu Alaihi Wasallam) - asked Rasulullah r: “Which person is most beloved to you?” Rasulullah (Sallallahu Alaihi Wasallam) replied: “Aaisha”. The Sahaba (R) thereupon enquired, “Who is the most beloved to you from amongst the men?” Rasulullah (Sallallahu Alaihi Wasallam) replied: “Her father” (i.e. Abu Bakr Siddeeq t) (Mishkat Vol.2 Pg. 555)