iCloud family invitation problem

The reason that it says is that you are all Family organizers is because you are all using the same Apple ID. You can’t share an Apple ID and then use iCloud for Family Sharing Storage. Family Sharing and iCloud Storage Sharing requires that all members have their own Apple ID and iCloud accounts.

You should set up Family Sharing and go from there.

Family Sharing - Apple

You’re welcome. FWIW, my family shared an Apple ID for years. We switched over to Family Sharing about six months ago. It wasn’t nearly as intimidating or difficult to transition over as I thought it might be and things have gone very smoothly since.