The gorgeous actor and his wife Yessica welcomed son Hunter Lee Holloway earlier this year – but managed to keep his arrival a secret until now.
Josh confirmed the news to The AP by saying: "He's here, he's upstairs. Six weeks."
He added that he and Yessica – who married in 2004 - are "calmer" this time around, joking that with four-year-old daughter Java they had "definitely [been] full of fear."
Josh, 44, was certainly looking pretty happy while attending a Lost anniversary event in Los Angeles this week.
The star, who played rugged Sawyer in the mystery series, joined the show's runners and his co-stars on Sunday night (16 March) to mark the iconic programme's ten-year anniversary.
(We know, TEN years!)
Josh can next be seen in crime drama Sabotage, co-starring Arnold Schwarzenegger and Sam Worthington. It's about an elite force who find themselves targeted after taking on a drug cartel.
Josh isn't alone! More celebrities to have welcomed babies in 2014 below!
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