One area I see lots of growth in and that I thoroughly enjoy is Brian's play skills.
I'm not saying that Brian still doesn't love to just go in his room for hours to "play trains": line up trains and push them back and forth, back and forth. Because he will do that at least once a day still. However, he is adding new play to his repertoire.
Take for example this:
We were at Corbin's first baseball practice when Brian pulled the hat over his eyes and then would "accidentally" walk into us (though it was apparent he could still see) and say "Oh sorry hahahahahaha".
At the same practice he stopped his incessant running around in circles to kick a ball around and stayed with it for at least fifteen minutes. When a toddler came over to join Brian gave him the ball and said "ball baby" and then squeezed his cheeks. Yes, he likes to squeeze cheeks.
Then there was this afternoon when he walked into Corbin's room and saw that Corbin had some sort of immense battle scene set up in his room with pirates, knights, robots, dinosaurs, and zoo animals. Brian picked up two dinosaurs, made them run around in the air, and said "Rawr, rawr, rawr." I acted scared and he chased me around the house making his dinosaur sounds and giggling.
Then I have this cute picture:
The astounding thing about this picture is that my niece Alyssa sat down first. Brian doesn't generally try to join people in anything, without being prompted to. Alyssa didn't ask him, he just joined her and they happily played dominoes together.
They became such good friends on this particular day that he allowed her to put an apron on him.
It makes he happy to see him playing with his cousins, whom he all too often, just ignores. Even if it involves him wearing a pink cupcake apron.