So, I just got an iPod touch from a family member who used it for like couple of months, but somehow (even after resetting it) their photos that they take using their iPhone sync into my iPod photostream. And I need space on my iPod, so if I deleted all the pictures from photostream, will it delete pictures from their iPhone? I don't want to delete any of their items. I'm totally confused as to why it keeps doing that even after all this time.
Check and see whose Apple ID is being used by iCloud. Go to Settings -> iCloud -> Account. The Photo Stream associated with your device should be the one associated with the iCloud account that is logged into the same device.
Also, deleting items from the device will delete them from whichever user's account is associated with iCloud on the device.