Garcia is suing Joby Harte and his company, Hot Rock Media, claiming Harte raped and sexually assaulted him dozens of times throughout his teenage years ... beginning when he was just 12.

The singer, now 20, claims Harte used the "well-worn pedophile playbook of grooming and seduction." Garcia claims it started with Harte promising him the world ... before showing him porn and then allegedly sexually assaulting him.

In the docs, filed by attorney Ben Meiselas of Geragos and Geragos, Garcia -- who auditioned for season 3 of "The X Factor" and joined the boy band at Simon Cowell's invitation -- claims on multiple occasions Harte got him blackout drunk. Garcia claims he'd wake up naked the following mornings next to Harte.

Specifically, Garcia alleges Harte organized a 2-night "songwriting session" back in 2014 for the band without parents at Catalina Island. Garcia says Harte got him drunk on tequila and vodka before he blacked out. Again, Garcia says he woke up naked on Harte's bed.

When Garcia asked what happened, he says Harte told him he undressed him and bathed him because he was covered in vomit after blacking out.

For his 17th birthday, Garcia claims Harte got in his shower stall at a hotel resort and forced him to masturbate Harte until he ejaculated. Garcia says he never told anyone about the alleged sexual assaults because he was afraid of losing his career.

Garcia is also suing two other men, claiming one former agent sucked his toes after a 2014 hangout with Harte ... and accuses a manager/producer of grabbing his penis during a 2016 concert in WeHo.

Garcia -- who also costarred in over 30 episodes on Disney Channel's "Best Friends Whenever" -- says he and his mother finally confronted Harte ... claiming the ex-manager had no visible reaction but did not deny it. Garcia claims Harte admitted he "did not behave like an adult."