Colorado family laws usually assign biological parents different parental rights and responsibilities. However, in some situations, a biological parent's rights may not be recognized, particularly for a father who is not legally married to the child's mother.
When a child is born to unmarried parents, Colorado law automatically recognizes only the mother's parental relationship with the child. An unmarried father's legal rights will not be established unless the mother identifies him as the father or a paternity test establishes him as the father. In Colorado, natural fathers are identified if the couple is married when the child is born or their marriage ends within 300 days of the child's birth.
Colorado law also takes into consideration cohabitation and any attempted marriage of the child's parents. For example, if the child's mother and a male individual try to marry but for some reason do not succeed in fulfilling the statutory requirements for a valid marriage, the male person could be declared as the natural father. The same applies when the child is born within 300 days of the parents separating after cohabitation. A Colorado man can be named the natural father to a child if he acknowledges legal ties to the child in writing or by filing a document with the state's Registrar of Vital Statistics.
A Colorado man can also be declared the biological father if he is listed as the father of the child on the certificate of birth or if he is required to provide financial support for the child based on a court order or written voluntary promise. Natural fathers are also determined by means of a paternity test that shows that there is a 97 percent or more probability that the man is the biological father.
Source: Childwelfare.gov "The Rights of Unmarried Fathers," accessed Sept. 1, 2014