Can't get into Realms on Minecraft: Java Edition? Due to GDPR (http://minecraft.net/privacy/gdpr/ ) users under the age of 16 need parental consent to play on Realms. To set up parental consent on an account, visit http://minecraft.net/update-account .
I'm sorry for the trouble you're experiencing with Minecraft on Xbox. For questions about the Xbox edition of the game, please visit https://twitter.com/xboxsupport or http://support.xbox.com . ^SA