This is their job. They make money monetizing their videos on youtube. I'm sure she's accepted the pranks as a necessary part of her life, and mostly gets angry because that's what makes a good video. In fact, I'm sure if anything actually happened to their kid she would assume it was a prank.
So... did his first wife die? I mean, call me crazy but I can't see this guy winning a custody hearing. I think she is probably his wife, either that or a prank must have gone really wrong a while back.
...did the people not hear that it is his girlfriend not his wife...they aren't getting a divorce they're just plain ol separting and figuring out who gets custody of the kid [girlfriend with the advantage on obtaining the kid]