And then he can begin inquiring into their true names. It seems just crazy enough to be true and if it is true, does one lead them or are they more of a cohesive unit? Let's say they do have a leader and there is one Joker that reigns supreme.
Many comics have said that Sans is the older brother... But I haven't gotten any proof yet. It makes sense that Sans could be the older brother... But it makes just as much sense that Papyrus could be the older brother.
Sans is one of the major antagonists of Underfell AU. He is the brother of Papyrus and takes on an appearance similar to the Sans of Undertale. Sans is a skeleton, probably born in Snowdin, who is pushed around by his younger (though significantly larger and more durable) brother Papyrus, to the point of being forced to call him boss..