I need a reason for a husband and wife to break up.
They have a 5 or 6 year-old daughter.

Something other than cheating or money or family. It needs to be all his fault. Something so bad that they end up getting a divorce.

All suggestions are greatly appreciated, thanks.

Maybe there was an accident or a car wreck or something like that where the little girl was injured. It could have been like the straw that broke the camel's back for the mother, i.e. he always has to be right and he's never done anything wrong in his mind, so he blames it on the mother and tries to get her to think of it that way too, only she won't stand for it and files for divorce.

The two biggest categories that come to mind is, he hurts someone else in some way but then instead of coming clean and doing the right thing, he badmouths the other person or lies to people well enough that they believe him and not her. For example a hit-and-run car accident, or tells everyone that her brother is a drunk who has been in and out of jail, just when he's been trying to turn his life around. Or maybe she's trying to get a new job, and he sabotages her in some way - not letting her have the car for interviews, or tells someone that works there that she's a flake and doesn't do a good job.

There could also be things with what he does at work - maybe he takes a job that is so far away that he has to live there during the week and only comes home on weekends. She ends up having to do all the housework, child care, etc. It's not so "bad", but maybe he doesn't want them to move closer to where he works (for whatever reason), and he won't give up the job either. In other words, she doesn't like the situation, but he won't change it.

Or, he tells his parents they can move in with them. Without her consent.

He might be a hired mercenary. Specifically, an assassin-and doesn't tell his wife. I'd be pretty creeped out sleeping next to a killer-espically one who does so for money.

Or, in that same vein-he could be a serial killer. AFter all, how many people have said, "oh-I never would have imanganged him to be that type of person" in regards to interviews about living-or knowing a serial killer?

He could have a past life he never told her about... assassin, or previously married - has other kids... he could have been to prison for a heinous crime but got let out for giving inside information on another cellmate.

I say make him a thief. He could be stealing from the wife, or raiding their 401k behind her back. He could be embezzling from his work place. Anything really.

Barring something illegal, perhaps he converted to some extremely different religion than what they were both practicing before, and it went against everything she believed? Like he suddenly wanted to try polygamy, or ask her to join a commune or wear a burka. Something she was definitely not going for. ESPECIALLY if he became convinced she would be punished in the afterlife somehow if she didn't convert fully with him.

Or due to some new group of friends or negative experiences, he had become more and more racist/prejudiced over the years, and she didn't want his hatred spilling into their childs life as well?

Ummm...Let's see... He could be one of those workaholic type guys, who just spend ALL their time working... Taking extra shifts on nights and weekends... He's never at home, he never spends time with his kid or wife, and she starts feeling unappreciated, unloved maybe even abandoned... Till it gets to a point where she gets tired of coming second to pretty much everything in his life, and, due to his absence, she starts to fall out of love with him. Next thing you know, he's hit with divorce papers. Bam. :)

Abuse. Emotional, physical, sexual, all three... take your pick.

I have a freind who is currently going through a divorce with her husband because he beat her dog to death with his bare hands. Well, basically because he's unstable and she doesn't feel safe with him anymore but that was the thing that best illustrates this feature of him.

drugs
gambling
mental illness
political ambition
job relocation
any serious act of hostility or destruction
new religion