A Microsoft file hosting and synchronization service.
As of today, Microsoft has not publicly disclosed the specific eligibility requirements or the list of supported countries for the transitional bonus storage. This is still a fairly new development. I suggest that you bookmark this page, so you can check for update https://support.microsoft.com/en-us/onedrive/changes-to-microsoft-365-storage
Since your family already exceeds 2 TB, I would start making independent backups rather than waiting to see whether the bonus applies. You do not need to remove everything from OneDrive immediately.