Paris was King Priam and Queen Hekuba's son. His mother had a dream just before his birth in which she gave birth to a fiery flame. The seer Aesacus interpreted this dream as a prophecy of Troy's demise, and he declared that the boy would be the ruin of his motherland.
On the day of Paris's birth, Aesacus stated that the child born to a royal Trojan that day would have to be killed in order to save the kingdom, as it would be the kid who would fulfill the prophecy. Though Paris was born before midnight, Priam spared him; Hecuba, too, was unwilling to kill the boy despite the urgings of an Apollo priestess named Herophile. Rather than that, Paris's father convinced his head herdsman, Agelaus, to remove and murder the child. Incapable of using a weapon against the child, the herdsman abandoned him on Mount Ida, believing he would expire; nonetheless, he was nursed by a she-bear. Returning nine days later, Agelaus was astounded to discover the boy still alive and brought him home in a backpack (thus the name Paris, which means "backpack") to raise as his own. He returned to Priam with a dog's tongue as proof that the act had been completed.
Paris's noble origins were exposed by his extraordinary beauty and brilliance; as a youngster, he defeated a group of cow thieves and returned the stolen animals to the herd, gaining him the surname Alexander Oenone became Paris's first lover during this time period. She was a nymph from Phrygia's Mount Ida. Kebren, a river-god, was her father (other sources declare her to be the daughter of Oeneus). She was gifted in prophecy and medicine, which she learned from Rhea and Apollo, respectively. When Paris eventually abandoned her for Helen, she advised him that if he was ever wounded, he should seek her out since she was capable of healing any ailment, even the most grievous.
Paris' primary diversion at this time period was pitting Agelaus' bulls against one another. One bull began to consistently win these matches, and Paris began pitting it against competing herdsmen's prize bulls; it annihilated them all.
Finally, Paris promised a golden crown to any bull capable of defeating his champion. Ares rose to the occasion by transforming into a bull and handily winning the match. Paris bestowed the crown to Ares without hesitation; it was this seeming integrity of judgment that inspired the gods of Olympus to appoint Paris as arbitrator of the divine struggle between Hera, Aphrodite, and Athena.
References.
Graf, Fritz. Greek mythology: An introduction. JHU Press, 1996.
Nagy, Gregory. Greek mythology and poetics. Vol. 2. Cornell University Press, 1992.
Rose, Herbert Jennings. A handbook of Greek mythology. Routledge, 2004.