Suggestions on fixing this Island.

About 3-4 years ago my girlfriend had someone local build her an island for her kitchen. After a year things started to get wonky with it. The wood has twisted at opposite corners. I have tools and I'm fairly handy, but I'm just at a loss as to how I can draw these corners back in. The wood has split on one board, which isn't really a problem yet, but I was also wondering what I can do for that. Maybe some sawdust and glue to fill it in? Any suggestions are appreciated, thank you.