Three of Squire Trelawney's four named servants accompany him on his voyage to Treasure Island. He leaves one behind, Mr. Blandly, to send another ship after them if they don't turn up in Bristol by August.
As for the other three, have you ever heard the term "redshirt"? In science fiction-speak, a "redshirt" is an expendable character. These guys are basically just around to die so the main characters don't have to. The reference is to the red-shirt-wearing guys in the original Star Trek series, who accompanied the command team down to various uncharted planets. Whenever the show's producers wanted to convince the viewers that the monster of the week is really dangerous, they would kill off a redshirt. Another, perhaps less geeky word for this idea is "cannon fodder."
And that's pretty much what Squire Trelawney's three servants are: perfectly nice, respectable gamekeepers and valets who wind up getting killed on the island to demonstrate how dire this pirate situation is. The one with the most personality is probably grumpy, loyal Tom Redruth, whose violent death is the one of the more emotional scenes of the novel. (See the our thoughts on Squire Trelawney for more on this moment.) But Joyce and Hunter are pretty much the same guy, so far as we can tell. There isn't exactly a lot of character development going on here.