Aesacus told Queen Hecuba she had to kill her newborn son, because he would be a downfall Troy.
Ageelaus, the chief herdsman was called to deliver the baby to Mount Ida and kill the baby, but he couldnt. So he left the baby.
That night a bear found the baby and took pity, so she kept the baby that night and took care of him.
Fast forward many years to Paris's adulthood. He offered a challenge to anyone to try and defeat his bull in a fight, so Ares accepted. Of course Ares won, but Paris kept his word and gave Ares the reward. The gods saw this and understand he was a man of his word.
The gods then asked Paris to choose the fairest of the ladies. It was between Athena, Aphrodite, and Hera. Paris was attracted by the beauty of Aphrodite and choose her. He was awarded wit the love of the most beautiful woman in the world.
Paris stole the heart of Helen, and took her away from King Menelaus, who was furious! He vowed to have the land of Troy destroyed, which then started the Trojan war.