Separate telling someone from publishing
Telling a relative something does not necessarily mean you want the same information posted publicly. Discuss names, images, location and health details separately. State your preference in concrete terms. People may have different assumptions about privacy, so explain the boundary that matters to you rather than relying on everybody to interpret a broad request in exactly the same way.
Communicate a changed preference
A preference may change after the first conversation. Tell the people concerned which sharing arrangement no longer works, and review the removal options in the service involved. Closing a link does not ensure that downloaded copies disappear. Keep the conversation focused on an explicit next action instead of assuming everybody already knows what a changed preference requires.
Your next little step
Choose one idea that suits your family and try it at your own pace. Every family has different needs.
An example in practice
For example: We shared the news with you privately; please ask us before putting the photo in a group or public account. Adapt the wording to your relationship and circumstances rather than treating the example as a required script.