Some people in the Bible had children, some didn't (examples: Jesus, John the Baptist, probably most of the apostles, Samuel, Samson, etc.) so I don't think there is a hard-and-fast rule about whether you should or should not have children, or how many. I think that's something that should be prayed about and also approached practically. For instance, I do not take great joy from being around children. Thus, I will probably not have many kids - two at most, but even that's a bit much. Of course God may end up giving me no kids, or 10. His will be done in these things, of course, but human activity does play a role.