First off, it's none of your business and you might want to do some work on yourself to understand why you are so passionate about someone else's life.
Second, your description sounds very slanted. The reason why, in the past, custody was skewed towards women was because of the conservative, sexist notion that women were better suited to hearth and home and men were the sole breadwinners.
Also, you never know what's really going on behind closed doors. The story he's telling makes him sound totally innocent. That may or not be the case.
Last, it sounds like your friend needs a better lawyer.