DS1 (3+) turned this month. He's like 20 lbs, but way tall and lanky. I didn't have to, but just decided it was annoying to hear "I see a firetruck" from a RF kid, then have the FF kid reply, "YOU"RE LYING! There definitely is NOT a firetruck near us!" And so on. Having them seeing the same things has definitely helped us keep the peace in van...until DS2 is verbal and will start arguing with the bigs.