If there is e-mail you need to drop your person on the computer to get them to read it. Also it helps if your person wants children (or at least is open to the idea) for them to be more likely to actually go try for children and not argue about it. ALso I found that people being happier are more likely to want children and there is also a shot you can buy in the medicines section to make conception more likely.

I don't know if age is a factor for men, but it is possible there might be a upper age limit on when women can have them (unless the baby shot helps that too).