What rights does the father have

My 20 year old sister is three months pregnant. The pregnancy was the result of a mistake she made with a 20 year old guy she hardly knew. She had planned to have the baby and give it up for adoption, but now there may be a problem. She just recently got in touch with the father and she was hoping to get him to agree to the adoption, but he refuses. He says that he wants custody and that he'll get it because he is in the airforce. My sister doesn't think he even cares about the baby, because he initially asked her to get an abortion. I have so many questions. What rights does he have? What rights does she have? How far could this actually go? Will he get custody simply because he's the natural father? What are the laws in Texas regarding this? Have there been past cases where an adoptive family was given custody over the natural father? HELP!!!!