I think the solution is probably to make having children more attractive with government subsidies and labor laws. E.g. free daycare, affordable education (including college), health care, a minimum amount of paid time off per year, etc.

Nobody should be forced to get married or have children if they don’t want to. But if we can alleviate some of the risks/down sides to having children, I think we will see more people choosing to start families and also having more children per family.