In Texas, as in many other states in the nation, a man is declared to be an "adjudicated father" if a court of law declares so. A man's paternity can be called into question for many reasons. Problems like this are exacerbated for unmarried fathers.
According to Texas law, a man is considered a child's father if that man was married to the mother during childbirth, whether he is the biological parent or not. The man would also be considered to be the father if the child was born before the 301st day of the marriage's termination. Other circumstances where a man's paternity can be established are when a man married the child's mother before the child was born, regardless of whether the marriage was declared invalid.
If a man has voluntarily declared his paternity, whether or not he has married the child's mother, the man is considered to be the child's father. The man's declaration of paternity must be recorded in the Bureau of Vital Statistics.
If the man promises to support the child as his own, the man's paternity is established. And if the man has been living with the child for the child's first two years and he has called himself the child's father, the state of Texas acknowledges the paternity of the man.
If a man wants to be absolved of his paternity, he must register with the registry of paternity. He must do that either before the child's birth or within a month after the child was born. Also, the mother and the man may sign an acknowledgment with the intention to establish paternity. This acknowledgement must be on record with the state.
Source: childWelfare.gov, "The Rights of Unmarried Fathers," Accessed on Nov.11, 2014