As of Minecraft Bedrock v1.16.1 you can kick or ban Minecraft Realm members if you are the owner of the Realm. Operators can only kick a player at the time of this article. You can remove/ban members via the member list in the realm settings, player list while in the realm or commands.

Member list

You can quickly remove/block members via the member list in the realm settings. Removing members will allow a player to rejoin if they have the share link/code. Blocking will not allow a player to rejoin until they are removed from the block list.

Click realm settings in the Worlds tab.
Click the “Members” button on the left to see the realm member list.

Click the minus button next to the member you want to remove.
Click Remove or Block from the options.

Player List

You can quickly remove or block a player while actually in the realm by accessing the player list.

Click pause, esc, or the menu button.
Click the player permissions button next to the player you want to kick or ban.

Commands

Click /, chat or right on the dpad
Type /kick gamertag then reason or message (remember kicking allows the player to rejoin if they have the share link/code)

Here’s the video I made if you want to see the commands in action. Drop me a comment if you need any help or have any further questions. I’m FNT, peace!