What's bothering me

So my brother really likes this girl. She was his first kiss and claims that she wants to date him, but after he gets back. He left for basic and ait training for army national guard. A few weeks after he left she got a boyfriend. She's 18 and her boyfriend is still in high school and can't even drive yet. He's 16. I tried to tell her not to hang out with the boy and lead him on and she did then they started dating. Anyway they broke up after not too long. She just found out she's pregnant. My brother doesn't even know because he's away. My brother really likes her and I feel like this will break his heart. Idk I guess I'm really protective over him.