Personally, I would keep quiet about the whole thing. What will you do if he says 'no, we are not planning to have a family'? What if they are trying really hard and are desperately unhappy that things are not going right for them? Perhaps there are problems about which you know nothing, and they do not want you to either know, or worry about. If they are planning to have a family, and everything is working(?) then it will happen in their time, and when they are content with it. Sorry if that sounds blunt, but we had one or two remarks about the amount of time we took to start a family, and I had to hold my tongue on several occasions. My daughter and son-in-law were married for 15 years before their son arrived - it was their choice.