We don't really spend time a lot with other kids than DD and most of her friends are older than her and quite advanced them selves.
Yesterday two kids were visiting us, one of them almost 4 so over 1.5 years older than our 26mo old DD. They have played together very well since we got to know them when DD was 12 mo and the boy 2.5. I just always thought that was normal. The little boy has younger sister 19mo and I was fully expecting all 3 of them playing together now as DD is closer to age with the sister than the brother. It really opened my eyes when the little girl (19mo) just walked around looking at toys when DD and almost 4 year old were playing shopping. The 19mo old did not really even try to have any contact with the other kids and DD calls her "Baby".
I also made ton's of mistakes during the evening starting of giving the 19mo old a glass to drink from (DD has been using a glass since 14mo) and asking the almost 4 year old to hand me over an "a" (they were playing with see and spell). DD of course started loudly complaining how there is no place for z, x or y and mommy needs to help her write words with them. Then I gave the boy the most difficult puzzle we have and DD the easier one and Dd first build her easy one and then went and build the other one too. Just before that the mom offered me that Dd could get some of their puzzles that are too easy for their son and too hard for the little sister...
The worst thing is that the little boy has a very advanced vocabulary for his age so I always though he was like our DD. The mom told me how funny it is that the boy seems to like DD best of his friends even that DD is so much younger and he usually prefers boys. He wants to marry her, DD is not convinced yet
