In Massachusetts, a person who is married within 300 days of the birth of the child to the mother is the legal parent of the child even if they are not the biological parent. This is a presumption that can be overcome with a paternity test. However, even if the paternity test proves that the husband is not the biological father, this does not necessarily mean he is not the legal father. Someone who acts like a parent for a period of time long enough for the child to be attached to them as a parent has certain rights and obligations. The best interest of the child require that a "de-facto" parent continue to be involved in their life (i.e. have custody and visitation rights), and in some cases also pay child support.
Even absent a marriage, if a father signs a Voluntary Acknowledgement of Paternity and is added to the Birth Certificate, then they are presumed to be the Father. After one year passes it becomes almost impossible to undo this legal acknowledgement of parentage. In the case of a faked paternity test or other fraud it might be possible to have a Court undo the acknowledgement even after the one year period. However, in many cases, as was the case with Mr. Kerkorian, the father has now been involved in the child's life and would be considered a "de-facto" parent anyway.
Although, California law may be different than Massachusetts law regarding these types of cases, it is still refreshing to see Mr. Kerkorian willing to pay significant child support and take responsibility for a child that is biologically not his. Of course, this reinforces what we've already learned from so many other non-traditional and adoptive families: You don't have be genetically related to a child to be a good parent.