Petyr Baelish, otherwise known as Littlefinger, was born to a lowly house of the Fingers, a region of the Vale. His family had little money or power, and after his father fought with Hoster Tully and became close friends, Petyr was sent as a boy to be raised at Riverrun. There, he developed the nickname Littlefinger, in reference to the little lands his family possessed in the region know as the Fingers. As a young age, Petyr fell in love with Catelyn Tully, but she never loved him back the same way, though her sister, Lysa, loved him very much.
Lord Baelish has spent most of his life trying to transcend his lowborn status and his intelligence is only rivaled by his ambition. In particular, he developed a strong mind for finances and accounting, and after several dealings, ended up in King’s Landing as Master of Coin to King Robert. At the same time, he opened up many brothels around the city and not only grew his personal wealth, but also power and influence within the city. Despite his love for Catelyn, it was Lord Baelish who betrayed Ned Stark, after Ned approached him with the truth about the incest surrounding King Joffrey and the illegitimacy of his claim to the throne. Littlefinger promised to help Ned secure the Kingsguard after Ned made these claims public, but instead, Littlefinger went back to the Lannisters and informed them of Ned’s intent. And so, when Ned proclaimed the truth, he had no backing, and the Kingsguard of the Lannisters turned on him, arrested him, and this led to his eventual death.