Lando and Han
Lando won the Millennium Falcon in a game of Sabacc. At the time, he was not an amazing pilot, so he hired a young smuggler named Han Solo to teach him. He later entered the sabacc championships, and lost to Han Solo. Han made off with the Millennium Falcon.
Prior to the Battle of Yavin, Lando aids Han Solo, Chewbacca, and Solo's old flame Bria Tharen in a raid against the Hutt controlled slave world of Ylesia. Beleiving they would be rewarded for their trouble they agree to help. Commander Tharen and the Rebel troops however double crossed their smuggling allies and took all the spice for themselves. Han was branded an accomplice and a traitor and Lando swears to never see him again.
Together, Solo and Chewbacca continued with the smuggling trade and gained a reputation among the best in the business. However, their ship was intercepted and boarded by the Imperial Navy during one particular run off Kessel, forcing Solo to jettison his cargo to avoid arrest. The result was crime lord Jabba the Hutt putting a bounty on his head. Han then meets up with Luke Skywalker and agrees to transport him to Alderaan, thus begins Han's connection with the Rebel Alliance.
Later, Lando won the mining facility of Cloud City keeping his operations out of the eyes of the Empire. Han seeks refuge there for repair to the falcon. Lando betrays Solo, turning him into the Bounty Hunter Boba Fett who was working for Jabba the Hutt and was assisted by Darth Vader. After Lando himself was betrayed by Vader, Lando joins the Rebel Alliance and helps aid in a plan to rescue Han and destroy the 2nd death star.