Linking three accounts in one household

[craigrg12]

Hi there,
I currently have three separate amazon accounts (so everyone can stream their own music at once) using three separate echo dots in one house, I would like to be able to link all the devices together though so we can create a group to call the kids for tea or play music everywhere etc. I have linked two of the dots together via the my household settings but can't add a third. Is there any way to do this?
Any help would be great.
Many thanks