Hello @HulkBusterAJ, found this support page that goes into details about family sharing. Towards the bottom footnote section, it states that game and add-ons that were included with the game purchase will be available for sharing. Though some add-on content, such as in-game currency or subscriptions cannot be shared.
The footnote is very generic, so I recommend contacting the support team to see why some of your family members do not have access to DLC. There is a chance that your DLC fits in that category mentioned in the footnote that states it cannot be shared.
Hope this helps.
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