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6 January 2012, 10:52
The 'Sexy Back' star's relative said she wasn't allowed to say anything until after Christmas.
Justin Timberlake and Jessica Biel are engaged, according to the 'Sexy Back' singer's grandmother.
Speaking to Gossip Cop, Justin's grandmother Sadie Bomar said: "He called me on Christmas Day and told me he's engaged."
She added that she had been told not so share the news "until after the holidays" and that Justin's family think Jessica is "a very sweet girl".
Representatives for both stars have yet to comment on the alleged engagement. Justin and Jessica have been together since 2007, but split briefly last year.