(On the topic of siblings in the same house playing sburb) maybe it would make two copies of the house?

The problem with this is that, for the Game to ‘Clone’ the two houses upon entry, you’d need to have both players enter at the exact same time, and the game to actually decide that’s something it deals with by cloning the house. I mean it’s not impossible, but Client-Server Chains and Entry Times are never easy when it comes to Homestuck, it’s already hard enough to get one Cruxite Artifact before the countdown runs out, let alone getting two and activating them simultaneously.

That’s another thing, what if the siblings’ Cruxite Artifact do NOT let them enter at the same time? Dave had an Egg, which forced him to just wait for it to hatch. John, Jade, Rose, all of them had to physically do something but Dave’s was basically just another Countdown. If one of the Siblings gets that but not the other, or if BOTH of them get that with two different times, synchronization ruined. There’s a lot of variables to account with. By general rule of thumb, given what we’ve seen, just one of the Siblings would play the Game, with the other being relegated to a non-Player, Supporting role.

Still though, if you DO manage to synch it up, the house-cloning is a fun idea.