Not limited to developed countries either. Urban India has laws that are utterly stacked against men, a woman can easily destroy your life if she wants to and does happen. Trying to undo historical injustice does not mean skewing the system against an entire gender but that is where we are.
Men's weak standing in child custody cases is tied to the societal norms and practices that make men take less interest in their own children overall.
Ironically, this widespread disinterest in child care is what have allowed women to get these rights in the first place, because the late 1800's was certainly not a period of feminist dominion.
The 1800s were not a period of domination for either gender -- by any measure. Pretty much every era has been a period of domination for the wealthy and ruling class. Within that wealthy and ruling class (which accounts for less than 1% of the population) you may be able to have a discussion about gender, but the fact remains that the vast majority of men and women -- for all of history -- have been subjugated by the ruling class.