The age recommendations I used for my older son had to do with small parts as he tended to swallow stuff ( including a nickel when he should have known better). I also found with him he was generally close to the age ranges as far as interest and ability give or take a year.
For my younger son I kept him away from the tiny legos but other than that the age stuff didn't matter if someone else was playing it he wanted to even if someone was his partner to help the first few times (thinking monopoly when he was really too young to play and the next thing I know he doesn't need a partner).
