This question is answered differently under Michigan law than it is under the laws of States that have enacted the Uniform Parentage Act (UPA, and States that have some judicially created exception like the ones in the UPA. In Michigan the Paternity Act and decisions of the court of Appeals and the Michigan Supreme Court deny standing to all biological fathers (not husbands) when a child is conceived or born during a marriage.
Consider the most recent Michigan case, decided February 16, 2005 (Numerick v Krull). The biological father's rights were effectively destroyed when Mom wed someone else after she and dad separated but before the child was born. If this is a sham marriage used to cut off Dad's rights, what happens when or if Mom divorces this husband? In this day and age people often move and lose touch. Bio Dad may never know if Mom moves to a state where she can divorce Dad and he can disestablish paternity. Bio Dad may never have the opportunity to parent or co-parent his child.
While it's true that these cases result from messy lives, are family lawyers supposed to turn away and ignore what might be in the best interests of a child to avoid getting our hands dirty? I don't think so.
What the UPA does with respect to children born or conceived during a marriage is really no different from the analysis we do under the Adoption Code where efforts are made to terminate a dad's parental rights so the child may be adopted. There we look at the relationship of the father to the child. Has the dad formed a substantial parent-child relationship with the child and has he provided regular and substantial support for the child?
The importance of allowing biological fathers to have standing arises from recent efforts in Michigan to enact legislation that would deal with the issue of "paternity fraud." The proposed legislation would allow a male to disestablish paternity and escape financial responsibility for a child or children born during his marriage to his wife. If we amend the Act in this piecemeal manner, then what happens to the child(ren)? They may be left without financial support and paternal guidance, often from the only father they have known.
If Husband has known that the child was not his for an extended period of time (the UPA sets a limit of 2 years) and he has not challenged it within the 2-year period, then he would not be allowed to deny paternity. It's one thing to deprive a putative father the right to establish his paternity and quite another to then turn around and deny the child the father he/she has been raised by.
Moreover, what is so different about a child having a relationship with her father AND her step-father - with alternate weekends and holidays and summer parenting, in a "normal" family (at least 50% of Michigan children live in such a family) - and a child having the same kind of relationship with a biological father?
Two cases that illustrate how the individual facts should determine whether a putative father should have standing were resolved in California and serve to illustrate what would happen under the UPA - what cannot happen under current Michigan law.