Both kids are currently obsessed with Legos. I'd say 80% of their playtime is spent with Legos. This is a great thing, in that (when working correctly) its a quiet activity that both kids can participate in both independently and jointly. However, there have been many wars and battles fueled by Legos.
They were both fighting over specific blocks, so I bought another set. They're still fighting. Ryan tends to want to destroy what Brooke builds, and Brooke likes to take what she wants right out of his hands whenever she deems it necessary.
Brooke will get really into building something, and demand all the Lego people, or all the green blocks, or all the windows ... Etc. Ryan doesn't understand why she needs the pieces he already was playing with.
Brooke also gets very possessive of her projects, and often doesn't want her brother within a 10 foot radius. Both kids hurry to finish every meal to get back to the "blocks" (as Ryan calls them). Not for the love of building, but for the race to protect his/her own stockpile and current construction project.
So, when they're both playing quietly, it awesome. When they're playing together and cooperating, it's honestly one of the joys one gets to experience as a parent. But for those Lego Wars (which seem to erupt often) I have the urge to take all of those little plastic pieces and chuck them out the window. But before I can start packing them all up, a truce is called and everyone is happily creating once again.