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Reality TV star Kourtney Kardashian's alleged one-time lover is taking her to court in a bid to prove once and for all he is the biological father of her four-year-old son.

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Michael Girgenti is hoping a judge will order an official DNA test, which will end the debate about young Mason's paternity once and for all.

Kardashian insists the Los Angeles-based model's romance claims are completely untrue and she revealed that a DNA test she requested in August proved her longtime boyfriend Scott Disick is her son's father.

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But Girgenti is calling her bluff, insisting he had unprotected sex with Kim Kardashian's sister in March, 2009, while she was on a break from her relationship with Disick.

He tells In Touch magazine, "I just want the truth to come out. At this point, I have nothing to say to her, but, if I am the father, I need to be slowly integrated into Mason's life before more time passes. If I'm not, I can rest at ease - and everyone can move on."

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He's hoping a judge will order an independently administered DNA test in court on December 16.