For privacy and safety of minors, we connect households. If your household is connected to another household, that household will see any photos you post of people in households you are BOTH connected to and vice versa.
For example, if you upload a photo of your nephew Jimmy, and tag him, the photo will appear in Jimmy’s "feed" or "folder". Anybody connected with Jimmy AND YOU will see that photo. If someone is just connected to Jimmy and not to you, they will not see that photo.