How to play minecraft realms or multiplayer?

Yes.

Among others he cannot play Minecraft multiplayer or Realms.

Here you can find some troubleshooting tips for Minecraft multiplayer:

Minecraft Realms and Multiplayer Troubleshooting

Hi

Are you talking about a Realm server or online multiplayer servers? Also, which version do you have? (Java or Bedrock)

Minecraft Realms | Minecraft

Minecraft mojang i dont now if realm server or online multiplayer servers

Hello, Juha. I'm Arturo, and I'll be glad to provide assistance with your inquiry today.

Do you have an active Xbox Game Pass Core or Ultimate subscription if you play on Xbox? (or the equivalent if you play on another platform, apart from PC and mobile phone)

This question is asked because it's a requirement on console to have the respective subscription that allows us to use online features on paid games.

“If you are playing Minecraft on a console, you will need to have an active subscription to your console’s network service:

Xbox Live Gold (Microsoft Xbox consoles)
PlayStation Plus (Sony PlayStation consoles)
Nintendo Switch Online (Nintendo Switch consoles)”

If your answer is affirmative, “You will also need to configure your Xbox/Windows Online Safety settings to allow Minecraft to communicate over the Internet and make sure that the Clubs and Multiplayer settings are both set to Allowed (click https://support.xbox.com/help/famil...e-online-safety-and-privacy-settings-xbox-one for more information).”

Reference link:
https://www.minecraft.net/realms/how-buy-realm

I'll look forward to hearing your answers.

Regards,

Arturo.

From Minecraft/Microsoft -

https://minecraft.net/en-us/article/minecraft-multiplayer-server-safety

“Join Multiplayer Games” Settings
If you have your settings set to block joining multiplayer games, you can’t join any multiplayer games in Minecraft, including shared local worlds, Realms or servers. To enable multiplayer in Minecraft, make sure this setting is set to ‘Allow.’

However, just like ASCllnaut, that setting was already turned on for my children. In other words I'm in the same boat, we can play on the LAN but not on a realm.