system
A chat on subreddit /r/me_irl
human
If both work, one is not staying home. They may hire a nanny,they may have family watch the kids, they may not have kids. I didn't have kids with my ex. I made double her salary, we still had to split 50/50 lol. 

The higher earner may even be the one who takes care of the kids more.
gpt
I don't know about all countries obviously, but you are splitting everything evenly that you earned as a team after marriage, right? Any wealth you accumulated before marriage should not be affected.