MY BRO-IN- LAW HAS A SECRET FAMILY

I'm going to try to make this as short as possible but right now I'm so upset 🙄😡 10 years ago my sister met a guy and she became obsessed with him I mean OBSSESED. She would follow him everywhere and he'll humiliate her over and over, call her names and tell her to go away. He already had a gf, but the girl was only in high school(my bro in law was 25 at the time and his gf at the time was 15) so nobody thought much of the seriousness of that relationship. Anyway, my sister insisted so much after this guy, that she ended up in his bed one night that he was drunk and she ended up pregnant. He  decided to be responsible and marry my sister even though he didn't love her. He made it clear that he wanted a life with his child no matter what. ANYWAY FASTFORWARD 10 years and him and my sister have TWO daughters and they live a "happy" life. She's always going out of her way for him taking him on expensive vacations and going all out for his birthdays. She's always remained kind of weirdly OBSSESED but they have lived a seemingly happy marriage. ANYWAY we just found out a few days ago that he HAS another family. YES. He got back with his high school gf 4 years ago and has lived a double life since then. They have a baby BOY and she's pregnant. They have an apartment a car, bank accounts(he's a business owner) and everything as a normal couple. She has social media and is FULL of pics of them together and studio family portraits 😱 my sister kicked him out of the house and whatever but she still lets him sleep over for the "girls" and hasn't filed for divorce because of "money" she's always making the girls call their dad and ask about what he's doing etc. she manipulates him with the girls. WE ALL CONCERNED about her because we think she somehow wants him back and is going to let him move back in. All those years that we suspected of him cheating he swore he wasn't. He has lied over and over and he's STILL with his gf. My sister says the gf is the "whore" that she got back with him on purpose with the intention of breaking her family. We tried telling her to move on, stop calling him, file for divorce already. She has hope he's gonna beg and ask to move back in, that he loves her, and that he's going to change. 😢🙄🙄🙄  what would you married ladies do on this situation? Im going to show my sis your comments and hopefully get her to see that she worth SO MUCH MORE. Thanks ladies!