My brother opened a Minecraft server!
When I enter the IP, Minecraft recognizes a server with 0/4 players online (although 2/4 players are online).
I can enter the server without any problems and move around freely.
If I walk to the coordinates where my brother's buildings are, there's nothing there!
When I send a message my brother doesn't get it, and neither does the other way around.
So I'm alone on a server.
I re-entered the IP a hundred times, there's no typographical error.
What can I do? In google nobody seems to have had this problem yet.
Depends on where your brother is hosting. It can happen that several servers are on one IP and are only separated by different ports.
Ask your brother for the port, then add IP: port to the server list.