I am a single mom and thought seriously about adoption when I was pregnant. I even had a lawyer(and still do) and met with several adoption agencies. The laws that I researched applied to Oregon, Washington, Idaho, California and Arizona.
First- I would like to know if he has been financially supporting the pregnancy.
If he has NOT financially supported any part of the pregnancy, and has been aware of the pregnancy, his participation is not required for her to adopt the child out. If the child is adopted out and he decides to petition for custody, he will have to prove to a judge how he would be a better parent than the adoptive parents, which would be hard to do if he did not financially support the pregnancy.
If he has been giving her money, or paying for any part of the prenatal care, then he has established parentage, and has a leg to stand on when filing for custody.
It is not like TV, where you wait for the DNA test to establish parentage. A simple interpretation of the law is- if you slept with someone and then found out they were pregnant, it is your financial duty to assume the child is yours, until proven otherwise by DNA. If the mother does not name him the father on the birth certificate or has hidden the pregnancy then the father can file a petition for DNA testing. Also, when I filed for child support from my child's father, the court assumed he was the father because I named him so, and sent him the affidavit to DISPROVE my claim, not to prove it. The father was given three choices on the affidavit, 1)sign the paternity papers to acknowledge he was the father 2)take the DNA test to disprove my claim 3)ignore the paperwork, and the court would assume he did not contest my claim. He chose to ignore the paperwork, and is now legally the father of my child. Even if he took a DNA test and it showed him not to be the biological father, he would still be legally bound to support payments because he had his chance to contest my claim.
Anyways, I am getting away from the point. Pregnancy is really hard and my heart kinda goes out to this girl. No offense to your brother, but it seems that he really is not ready for the stability that raising a child involves. He got a girl pregnant, and already has another girlfriend before the baby is even born to be dealt with? And this new girlfriend is magically the person for him to have raise his baby for him? He is not even married to her, and honestly, any judge would laugh at his petition. If he is really serious about being a parent, he should take parenting classes, and seriously think about what he alone has to offer his child. His girlfriend may not always be there, it is an extreme commitment to raise a child. Is this something he would still want to do if he did not have a girlfriend? Did he think to offer to help the mom with keeping and supporting her child, or is he just fighting to keep the baby if she adopts her out?
Honestly, I think the mom will end up keeping her baby. It sounds like your brother and the mom got into a fight, and she became scared of dealing with him for the rest of her life. I felt that way when I was pregnant too. I honestly felt I couldn't spend my life dealing with my child's bio-dad for the rest of my life. I was being selfish, and when I met my daughter all of that melted away. I understood that whatever I had to deal with was worth knowing her.
I think she is scared and is saying things out of fear. You can't sign adoption papers until after the baby is born. I think she will birth her child and meet her child and melt into motherhood.
ps-also, in Oregon you cannot "sign away" parental rights, but an adoptive couple/parent can adopt the rights and legal responsibilities.