My parents know that we are TTC, but I only told them after about two months into it. They knew we were going to start trying in May this year, but we moved it forward to Feb and didn't tell them. They then asked a couple of months ago when we would be trying, and I told them we already were.

My in laws on the other hand, don't know, and will only know once we are expecting. It's just different and they don't expect to know IYKWIM. But they would be excited though when and if we do announce.

I think it is a personal choice as to who you tell or if you tell anyone at all.