TMZ reports that Michael Girgenti claims to have fathered 3-year-old Mason after he and Kardashian had an unprotected sexual encounter in 2009.
In the documents filed by Girgenti, the model claims he met the reality TV star during a photo shoot in August 2008 and began a texting relationship with her. He adds that things took a turn for the physical in March 2009 when Kardashian told him she was "on the outs" with then boyfriend -- now still boyfriend -- Scott Disick.
Kardashian reportedly told Girgenti "she wanted to hang" and the two met and had "unprotected vaginal sex." The documents state that at the time of the encounter the model "ejaculated inside [Kardashian's] vagina."
Girgenti, who believes himself the father of Kardashian's first born son, said he figured it out after noticing a striking resemblance between the two and how he looks nothing like Kardashian's second child with Disick, Penelope.
In the documents filed in the L.A. County Superior Court, Girgenti requests joint custody of Mason in addition to DNA tests for Kardashian, Disick, Mason and himself. The judge has set a hearing for next month.
According to TMZ, Kardashian's lawyer sent a letter to the model telling him his allegations were "false and defamatory."