Separate names with a comma.
It says the reason when you try to log in. If you think the punishment is incorrect you can create an appeal at https://hypixel.net/appeal
Sadly you can not remove a player if your coop only has 2 players in total. If there are more players than 2, everyone else has to vote with...
Sadly, there is not much we can do without any evidence. You can still try to report the player at https://www.hypixel.net/report