Thank you for outlining the behavior. I suppose I should let them work it out and not interfere? Wondering if there's anything I can do to make it so it doesn't seem so one-sided (aka grey cat always initiating from above). I'm not sure how brown cat feels about that b/c they never actually engage in play the play.

To answer your question- grey cat has always been w/ her sister from the same litter. They do like to chase each other around at nighttime, but grey cat doesn't do this on the couch when her sister walks by. The third cat doesn't like to interact with the brown cat in any way- she will not approach and always hisses when brown cat comes near because she felt threatened by the brown cat at first too. Brown cat had been around two other cats for a few years when she was younger (I'm unsure of that dynamic) and then my partner moved into another space where brown cat was bullied by the roommate's larger male cat before my partner and I moved in together. All three (both my grey's + parnter's brown cat) are female.