The club has not confirmed the agreement with Melendez.
Melendez's father, Mervyl Melendez, said his son signed on Saturday and is now participating in minicamp in Surprise, Ariz. The Royals have also signed their first-round pick, first baseman Nick Pratto, according to MLB.com's William Boor.
With his father being a head college baseball coach his whole life, Melendez grew up around the sport. He displayed signs of wanting to be a catcher when he was 2 years old, his father said, by crouching down, putting a hat over his face like a catcher's mask and smacking a glove against the tile in their home to simulate the popping sound a mitt makes when a baseball is caught in just the right spot.