Raising kids is but one kind of life stressor and it's not the state’s job to "equalize" life paths by punishing those who don’t have children or want to pursue different goals. Instead, the state should ensure a strong safety net so people are free to find their own balance.
Some pursuits genuinely take a monk-like dedication to see breakthroughs and we shouldn't hobble ambitious people who want to undertake them in the interest of fairness. You're describing a world where someone can't become a viruouso cellist, pioneer a life saving neurosurgery technique or revolutionize computer architecture because someone else decides to have kids. That doesn't sit right with me -- it's a little too Harrison Bergeron.
People might want to throw themselves into intense work for a decade before changing direction and focusing on raising a family or giving back to their community. Or maybe they want to do that the other way, start a family first and then once their kids are adults they want to pursue dreams that they spent decades dreaming of. Flexibility and dynamism in life roles is part of a healthy society.
The role of the state should be to ensure that no one has to 60 hours a week to survive and to ensure that everyone has real opportunities to live their best life that they choose -- not to make that choice for them.