Cameron Boyce, who has played Cruella De Vil's son Carlos since the first Descendants four years ... unintentionally makes a rival of Sleeping Beauty’s kid Audrey (Sarah Jeffery).

“There are days where it shatters my heart,” says Jeffery, 23, whose character Audrey stars alongside ... that it will dedicate the Descendants 3 telecast on Aug. 2 to Boyce’s memory.