Before coming out to perform for the panel of judges, Cassidy sat down for a pre-recorded segment, where he opened up about his background.
"I come from a very musical family," Cassidy shared. "Growing up, everyone was a singer and everyone had their own careers. It's just been this searching and this struggle to find out who I was."
Cassidy has turned his life to religion and helping the less fortunate, and in turn has made soulful worship music his niche. He says he sees The Voice as an opportunity to help further his goals and "really carry on the family legacy."
His famous grandma also participated in the interviews, and opened up about her initial hesitation about having her grandson follow in the family's footsteps.
"In the beginning, I was not very happy with him going into show business," Jones admitted. "But, when I saw him sit down at a piano, I didn't even know he could play the piano. Then he started to sing, and I thought, 'You know what? This is a voice that's really remarkable.'"
For Cassidy, the biggest appeal of The Voice's blind auditions is anonymity, and getting the chance to prove his talent without the specter of the Cassidy name influencing anyone's decisions.
"I love that the coaches don't my name, they don't know anything about me," he said. "They're just judging me purely on the merit of my voice."
The young singer then took to the stage, where he performed Joan Osborne's 1995 hit "One of Us," while also playing the piano.
It took a minute for the judges to appreciate his vocal skills, but Adam Levine and Alicia Keys both turned their chairs
-- and Keys couldn't have been more excited to see that Cassidy was playing the keyboard.
Shelton explained that Cassidy could pull off an epic piano duet -- similar to Elton John and Billy Joel -- "if you had Alicia Keys as your coach."
"I feel like there are other combinations of instruments that could also take place," Levine shot back. "Like guitars."
Through all the judges' banter, Cassidy never volunteered the fact that he came from the famous musical family until Keys directly asked him about his musical background and how he got into singing.
After revealing who his grandma is and his ties to the Partridge Family, Shelton and Keys were suitably impressed, and Cassidy admitted that he's been singing "since I came into the world."
"He came out singing," Keys said, laughing.
Despite Levine's best efforts to win Cassidy to his side, it seemed like he had his mind set from the start, and he ended up joining Team Alicia.
Keys knows how to pull out all the stops when trying to win over contestants. Last week, the "Girl on Fire" singer even serenaded one contestant with an impromptu performance
that won her over to her team. Check out the video below to see more of Keys' secret Voice