Kourtney Kardashian has been issued with an ultimatum by the male model, who claims he had unprotected sex with her in 2008 and is the father of her son Mason.
Michael Girgenti recently filed a lawsuit against the reality TV star, but before he took the case to court he wrote an emotional letter urging her to submit the three-year-old to a DNA test, Radar Online reported.
In the note dated April 23, Girgenti wrote that his attentions are not to hurt the family Kardashian has created with Scott Disick, but at the same time, Mason deserves to know the truth.
He assured her that he will be a great father to the child.
Girgenti also urged to the 34-year-old to take the appeal seriously else he will be forced to take legal action against her.
He filed paperwork at Los Angeles County Superior Court last week in a bid to get joint custody of her child, and a hearing has been set for next month.
However, the 'Keeping Up with the Kardashians' star has denied the claims, insisting that there is no way Girgenti is Mason's biological dad, as they never had sexual intercourse.