Autism. Good buddies.
Bright Eyes' relationship with his brother Max is developing. They are still worst enemies at times, but those times are shorter and fewer, and there is much more actual play going on between them.
I love to hear them make swimming pools in the lounge room (don't ask... it was ok in the end), take their toys and their horses a secret way into a fairy cave, and do stuff together that takes actual coordination and repair. They have a real and developing relationship.
This kind of thing started earlier this year, but it never lasted very long. After 20 minutes or so, Bright Eyes would wander off, leaving his brother intensely frustrated, yelling, "Come back! Come back!" Now, however, it can last for an hour or more, and what is going on is normal 3-4 year old play. It's very exciting to see.