My brother and I can't play on mineplex together, we can never see each other or play on the same survival game as we somehow on different servers even if we try?
Mineplex is split into a number of separate servers, both in lobby and in games.
By using the Lobby Selector (clock) you can select the lobby server that your avatar will appear in.
By right clicking on the entity in front of the game type you want to play (whether Nether Skeleton for Mixed Arcade, or Iron Golem for Super Smash Mobs), you can see a list of available servers (where yellow is in-game, and green is undergoing sign ups/pre game).
Communicate with your brother which server you're joining, and both join the same one, and you should be together.
Since Mineplex is such an enourmous server, it has to has multiple different lobbies at a time, which means when you click into the server, it puts you into a random lobby, with different survival games servers, bridges servers, etc., for that said lobby.If you want to play with your brother, when you join Mineplex, ask your brother to select a lobby, for example, the bottom left one in the available lobbies. This should make it so you and your brother are on the same server. Then if you want to play on the same survival games server, just remember to select the same server as him. Hope this helps!