We know what's behind Kourtney's baby bump.

Kardashian family getting very necessary dose of testosterone.

Kourtney Kardashian's rep confirmed Friday that the star is expecting a little boy. The baby is due to arrive at Christmas. How is the family reacting?

They're psyched. Kourtney told E! News, "A boy is definitely needed in this family!" She said she and her boyfriend Scott Disick are "thrilled to add a little boy to the bunch."

Among the rest of the family, the news came as no surprise. Kourtney said her stepdad Bruce Jenner and brother Rob Kardashian knew they'd have another male in the family: "Bruce and Rob told me it would be a boy the whole time."

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While Kourtney's painting the nursery blue, sister Khloe's planning a prenup. Read about the details here. Plus, the Kardashian girls don't let domestic duties dampen their social lives...click here to read what we mean.

Plus, don't forget to check out our gallery of the Kardashian sisters, right here.

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