If the child was born or conceived during your marriage to the child's mother, you are presumed to be the father. This means no proof of paternity is needed. However, you can still fight paternity by filing a suit in court to disavow paternity.
To fight paternity, you must first file the lawsuit within one year after you learn, or should have learned, of the birth of the child. At trial, you must show proof you are not the father of the child. This proof may include:
negative blood (DNA) tests,
sterility (unable to produce children),
physical impossibility because of location at the time of conception, and
any other evidence the court allows.