I don't know how to help my brother

TL;DR at bottom of post

Okay so i dont really know how to start this but let me try to explain the situation.

So for like 2 years my brother and this girl have been dating online long distance and finally met for the first time last august. Honestly i thought she seemed really nice and super cute from the pictures he showed me and the one time i said hi to her while they were video chatting, i was just happy that my brother was happy, espcially after seeing the pictures he took when they met for the first time, id never seen him smile so big in pictures before. Then at christmas break she actually came to visit us for 3 days as my brother's gift for doing well in school (my brother and I are both in college, we live in canada and shes from southern usa). Of course we were all excited to meet her and go sledding or skating with her since she never really saw snow, but then she actually arrived. I was the most excited to meet her, i got a bunch of stuff ready for when she arrived and boy was i disappointed. For the entire duration of her stay, she stayed in the basement with my brother (his room as well as her spare bed is there) and only came upstairs to either use the washroom or eat supper. Then there was the Christmas eve service at church. Our family is christian so going to the service is really really important to us, but my brother ended up skipping the service to stay home with her because she didnt want to go(shes not religious). You can imagine how angry my dad was for that. I understand they wanted to spend as much time together as possible, but we never saw her. The most amount of time she was even in the same room as us were the times when she arrived, and when she was leaving. Honestly, i was pissed after she left, and kinda glad, you can probably tell from how salty i am about the whole thing(she left around 1am christmas eve so she wasnt there on Christmas).

Anyways like a month later we find out my brother failed his semester and i was like ??? and my parents were soo mad because 1. He kept telling them he was doing fine 2. He never asked for any help from my parents or guidance people from the college or anything 3. My parents paid for his girlfriend to visit as his gift for doing well in school, so he lied to them about it so she'd be able to come.

Skipping forward to a few weeks ago my brother casually brings up that shes pregnant while im driving him home, oh and shes due the first week of june. Thanks for letting me know sooner. Despite being really disappointed with how irresponsible my brother was for getting a girl pregnant (hes 21, shes my age aka 19), i got over it within a week and was just happy for him and excited i was gonna be an aunt :). Then today (fathers day) our family went downtown to look around the shops n stuff and i wanted to show my brothers this really nice crystal shop with pendants and stuff (its like a mix of expensive and inexpensive stuff, i mostly wanted to show them the 10$ crystal pendants in case they wanted to get stuff for their girlfriends or something. Long story short, my brother picks a really nice pendant (50$) for his gf, which i didnt care since i figured he was getting it for her as a gift for having the baby since he couldn't be there. My dad gets mad at him after telling him what he bought for her and i thought he was just overreacting again.

Later on me n dad go to the dog park and he tells me whats been going on. Basically he starts with how annoyed and frustrated he is with my brother for doing all this stuff and then he asks me if i knew the baby wasnt my brothers. I just stand there like whattttt. Turns out during the period between the end of august (which is when i thought my bro got her pregnant) and when she visited in december, she had sex with another guy in October or something and got pregnant. Meaning she knew she was pregnant when she visited at christmas and that she (cheated???) on my brother. The reason i say cheated?? is because i dont actually know what their relationship...is. Like i dont know if they were together or anything during that time or if they dont count it as dating since its long distance, all i know is that my brother is in love with her, but i really dont like her. How could they be so in love and then be apart from each other for like a month and then she gets pregnant from another guy. Oh and have i mentioned she hasnt even told the father she had his kid? What doesnt help either is that my brother told my dad they were just friends now after finding out she was pregnant, but he was still buying these nice gifts for her and even looked up colleges in her state as if he was gonna somehow be able to afford school in the US with no job and taking care of a kid that isnt his. My dad of course doesnt approve of this because he doesnt want my brother to ruin his life because of a girl that doesnt care about him. My brother told me he's gone on a couple dates/talked to a few girls while they were apart, but none of them can even compare to this girl so he just doesn't care. Makes it pretty hard to believe they're just friends. It's also fucking awful that while he can't even think about dating other girls because he loves her so much, she goes and gets pregnant and then expects my brother to come take care of it together and live happy little lives where neither have a job nor an education. I don't know how to help my brother, any criticism we say towards her he just brushes it off and says we're overreacting or just ignores what we say since clearly we don't know anything about true love. She's horrible for him and I don't want him to ruin his life for a girl that's just gonna cheat on him if they're apart for more than a week. He's a very kind and thoughtful boyfriend, but his emotions are clouding his judgement of the whole situation.

TL;DR: how do I help my brother realize he's in a relationship with a girl that doesn't love him