I think Texas has a law that considers you the father and treats you as such if you have not disputed the paternity of the child within a certain time frame (I think it's 1 year). If you act like the father and take on the responsibilities, you are, in the eyes of the court, the father, no matter what DNA the kid carries. Everyone married to a woman remotely possible of being a slut should carry a cotton swab and paternity testing kit just in case.