Kate Hudson's Costar Jokes About Impregnating Her

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Is Kate Hudson going to need a paternity test when she welcomes her second child later this fall?

Though the 31-year-old actress is currently 17 weeks along with Muse rocker Matthew Bellamy's baby, her Something Borrowed costar Colin Egglesfield joked that he may actually be the child's father.

"[She got pregnant] right around the time when we were working together, so they might want to do a DNA test when that baby comes out," he joked at Wednesday's Children Awaiting Parents bash in Hollywood.

Kidding aside, the 37-year-old actor tells UsMagazine.com he had a blast playing Hudson's fiance in the upcoming flick -- even if they didn't exactly become BFFs when cameras stopped rolling.

"We had a lot of fun on the set, but at the end of the working day it's not like we were hanging out as friends," he explained. "John [Krasinski] had his fiancee, Ginny [Goodwin] had her fiance, Kate's got her baby-daddy. After spending 14 hours a day with each other, it's like, 'I love you, but get out of my face!'"

Still, the actor -- who will also star opposite Kate Bosworth and Rachel Bilson in BFF & Baby -- tells Us he has the perfect baby gift for Hudson.

"Maybe a little kiddy drum set because, you know, she loves her rockers, so maybe a mini guitar," he joked. "Start 'em young!"