I know it may sound like you are jumping into this question too quickly but it’s going to come up at some point so it’s important to get it over and done with.
It is no good if you want children within the next year and they don’t want children for another five. Or maybe they aren’t even sure if they want children at all. Are you okay with this?
You both need to be honest. Some, perhaps for medical reasons, are not able to have children. Possibly, you yourself, aren’t able to sire children and if you know this for a fact, you need to inform them right away.
It could be you already have children and/or they already have children. So, in this case, are you prepared to take on this responsibility. And be honest with yourself, there is no shame in not wanting to bring up another person’s child. It is a huge responsibility so you must be fully willing and able.