Free Google Home Mini (White or Charcoal) for anyone who signs up to Spotify Family.
For Existing and New Users. Offer is only valid for the "primary account holder" of the family.
Existing users visit https://www.spotify.com/au/googlehome/register/ to register for your free Google Home Mini.
Register "your interest" at the above link and then revisit the link and you should be able to go straight to the Google Store to purchase it right after. (That's what I managed to do)
Terms & Conditions: