help, long read

My brother has lived with his dad most of his life, and my mother gets visits on holidays and the summer. This year, they switched the custody agreement. My brother went down to see his dad on Thanksgiving and New Year's. He had sex with this girl (who my entire family hates, she's a ton of drama and very much into playing head games). My mom took my brothers phone because he wouldn't wake up and was getting texts. It turns out the girl he slept with is pregnant. She says it could be his but she's slept with like, 5 guys besides him. plus, she has a boyfriend. My brother's known for 2 weeks and kept it a secret from everyone. It would kill him to let another guy raise his kid, but she won't admit to it being his. Legally, we have no idea what to do. She is in a different state. *update. My brother is 16, she's going to be 20. we're going to try to get a court ordered paternity test and threaten her with statutory rape charges if she won't let him be a part of the baby's life. She told my brother he could never be a part of the baby's life even if it's his. s