Consider the Dukkha of having a family before you start a family. If you do think of having a family, really think more seriously about the responsibility that it involves, about the hard work it involves, about the difficulties that may be encountered. Consider: What does a kid really need? What does a kid do? How does a kid get sick? How do they get injured? What about insurance? What about medical costs? What about schooling? Really consider it deeply if you ever think about having a family because it's not all fun and games. When people talk to us about this, we do encourage them to look at it more deeply.
Now, on another level, the Earth is getting crowded, there's no question about it. There are already too many people on the planet. That's something else to consider as far as having your own children. If you want a family, perhaps adopt a child who is already there wishing to have a family. That's just another thing that I throw out to people if they're thinking about starting a family.