Blackstock is the son of Narvel Blackstock, Clarkson's manager, and stepson of country singer Reba McEntire, who became friends with Clarkson after the women performed a duet on American Idol in 2002.
Clarkson signed with Narvel Blackstock's Starstruck Entertainment management company in 2007 following a feud with recording industry titan Clive Davis over the musical content of "My December," her third album.
Blackstock proposed to Clarkson with an engagement ring he designed with jewelry designer Johnathon Arndt.
"Everyone has been asking about my engagement ring... It's a yellow canary diamond with diamonds around it and Brandon designed it with Johnathon Arndt! They did an amazing job! I can't wait to make Brandon's ring with Johnathon as well!" Clarkson write in a follow-up tweet.
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