In my experience, once I moved in with someone that had kids and I started talking about family at work, it seamed like I got bigger raises and better promotions. Whereas pre-family, I was seen as "just a kid, a smart one, but still just a kid". After I was treated as an adult.
I partially felt the same, but you also go into negotiations with a lot more knowledge about life cost. Kids cost money. Daycare costs money. A car costs money. And you suddenly realize that your paycheck needs to cover a lot more than what it had to before. I felt much more comfortable asking for a higher salary, just because I knew I had a family to feed and not just me.
