Brenda Song, Trace Cyrus expecting baby

Miley Cyrus is going to be an aunt!

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The singer's rock star brother Trace and his girlfriend, Disney Channel actress Brenda Song, are expecting a child together, a source confirms to Us Weekly.  (Celebuzz first reported that Song, 23, is "about eight weeks along.")

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Song, who played against type as Andrew Garfield's psycho girlfriend in "The Social Network," first began seeing the ex-Metro Station rocker (who now fronts the band Ashland HIGH and has a clothing line, Southern Made Hollywood Babe) earlier this spring.

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"Trace has known Brenda through Mile for years but they were always friends," the source tells Us. The couple made their first red carpet appearance together at a Nylon Magazine party in May.

This will be the first child for Song and Cyrus, 22, who now live together at his apartment. "It was not expected," the source tells Us. "They were both startled to find out she's pregnant...They are figuring out how to handle it."