How do I fix my sisters marriage?

Ok so just the other day we found out that my sister and her husband apparently had a fight, he packed up his things, and left. I mean, what kind of couple doesn't do that? Every marriage has their arguments.. there were even a few times my parents did that but they came back! Anyway, so I think they are ending it to fast. I love my sister, but we are not SUPER close (shes 29, im 14..plus she is my half sister) I don't know what to do. As soon as he left they changed their facebook statuses to "single." or whatever. I don't know if they are willing to try to fix it or talk about it or what, but the thing I'm worried about is I think that my sister probably won't be giving it another chance because of the previous marriage. She said " I don't want it to end up like the last one." Her previous marriage was with a complete **** and stole stuff from her and all that. This other guy is NOT like that. He is my brother.. we all got a long so well. We all went on vacation together and he was like my big bro that I never had. My little bro (he is 11) played nerf guns and video games with him, and I would ATV ride (We both are big ATV riders) with him, my dad, some of my cousins, and uncles all the time in the trails. He also was going to help me pole vault (I pole vault in track, and so did he) And everyone got a long so well. He fit in perfectly.. he actually TALKS unlike the guy in her other marriage who freaked out when he saw a bug. What Do I Do???