As TMZ's noted, in the eyes of the state's Family Code, Kardashian's estranged husband, Kris Humphries, is presumed to be the father of her baby because the two are still legally married. Kardashian filed for divorce in October 2011 after 72 days of marriage, but it's not yet official.
A man is presumed to be the natural father of a child if he is or has been married to the mother, and if the baby is born during the marriage or within 300 days after death, annulment, declaration of invalidity, divorce or after a judgment of separation is entered by the court.
Humphries filed for an annulment and separation from Kardashian on December 1, 2011, but a judgment of separation hasn't been granted, making him the presumed dad. Anyone involved can clear up the paternity with "clear and convincing" evidence, such as a DNA test.