We have pretty much the same conversation with Ethan almost every day. Ethan asks us to play with him. Something like baseball or soccer. We comment that we are busy (not always, I do play with them a lot, as does Daniel, but sometimes we have to be grownups), but note that Vivian is standing next to him, asking him to play. He throws a fit, says he doesn't want to play with Vivian and cries that we are not being nice. I generally make a comment along the lines of "that's the reason there are two of you, so that you will each have someone to play with."
I am seeing things start to change though, as it finally dawns on Ethan that he can play games with Vivian that Mommy is not good at or is not willing to play. Case in point. This morning he grabbed three pairs of socks from the unfolded laundry on the couch, put them on, and declared that he was skating. Then he ran in circles around the living room (which is carpeted, so he wasn't even sliding). Vivian thought this looked like a brilliant idea, so she immediately did the same. And they laughed and played "skating" for quite a while, before moving on to the equally exciting game of "try to fit Mommy's shoes into a small styrofoam container that's sitting in the hallway!" Which also brought on great amounts of preschooler laughter.
I'm discovering in general that if I leave them to their own devices for 15 or 20 minutes, they generally come up with some sort of creative game to play. And no matter what Ethan suggests, Vivian is happy to follow along. I spend a lot of time being glad that he's the cautious one and is scared of things. Otherwise I'm pretty sure he'd be trying to get her to climb bookcases with him (the bookcases and tall things are all fastened to the wall, since we live in earthquake territory. But still.)
This is a trend I can embrace. I'm so much better at being a mom when I get a few minutes break from being climbed on or forced to play Candyland. Which brings up the question- "why are all kids' games so unbelievably annoying?" So glad that the grandparents show up next week. Grandparents HAVE to say yes to kids when they want to play Candyland endlessly. I think it's a law. :)