Maybe I’m not understanding what your asking but I’ll give you my take on this.
I got pregnant by another man while I was still married. According to the laws here in the State of Kansas, my husband is presumed to be the father even though both of us know he is not. I could have had him pay child support for my son even though he isn’t the father and there isn’t anything he could do about it. He could take me to court and prove he isn’t the father but because we were married at the time of conception he is considered the father. Doesn’t seem right does it? My fiance is going to adopt my son after we get married and my ex-husband will have to sign a document giving up all paternal rights… even though he isn’t the father and has never paid me a dime for him nor has he had visitation rights.
As for the OP, I don’t think it’s right that this man has to pay child support for a child that isn’t his but at the same time I don’t think it’s fair to the child to suddenly be without his father figure. Does this man still see this child or has he cut all ties?
There is, incidentally, a fairly famous U.S. Supreme Court case that deals with the constitutional implications of presumed fatherhood laws. Michael H. v. Gerald D., 491 U.S. 110 (1989).
Seems Husband and Wife were intermittently separated, with W going back and forth between H and the Neighbor. The result is a baby, who has W’s name on her birth certificate even though blood tests establish pretty conclusively that N is the biological father. N holds himself out as the baby’s father and helps raise her, but eventually H & W reconcile (H was French and W was an international model, after all ;)). H & W then cut off N’s contact with the child. N sued, but under California law, a child born to a married woman is presumed to be a child of the marriage, and only the husband or wife has standing to challenge paternity. In a split decision, the Supreme Court upheld the constitutionality of the law, which put family stability in a more favored position than actual biology.
Section 38-1115(a): (a) A child or any person on behalf of such a child, may bring an action:
(1) At any time to determine the existence of a father and child relationship presumed under K.S.A. 38-1114 and amendments thereto; or
(2) at any time until three years after the child reaches the age of majority to determine the existence of a father and child relationship which is not presumed under K.S.A. 38-1114 and amendments thereto.
I did not, in a relatively cursory examination of the KPA, see anything that would bar a presumed father from challenging the presumption of paternity at any time. As far as I can tell without looking into the case law, Kansas is pretty much wide open when it comes to challenging and establishing paternity. However, I do not know Kansas family law, so I may well have missed something. Check the KPA for yourself over at http://www.accesskansas.org/legislative/statutes/index.cgi by browsing through Chapter 38, Article 11.