Howie Dorough

Backstreet Boys' Howie Dorough had plenty to celebrate this week.

Not only did the singer ring in his 39th birthday on Wednesday, but he and his wife are expecting their second child.

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"Thanks to family, friends & fans for all the amazing birthday wishes. This year I'm receiving the best gift from my wife, another baby boy," he tweeted on Monday.

Dorough married his longtime girlfriend Leigh Boniello in December 2007. They welcomed their first child, James, in May 2009.

After welcoming back original member Kevin Richardson to the group in April, the Backstreet Boys have been working on a new studio album and are set to perform together on Good Morning America on Friday, Aug. 31.