There's a lot of things you'll need to check. If those pics were emailed to him you'll need access his email account and delete the relevant emails and/or if those pics were texted to him you'll need to access whichever texting app(s) he uses and delete those relevant text messages. And of course you need to use the photo manager app on your Tab and delete those pics there too. Also there are online backup/syncing services like Google Drive, Google Photos, and Dropbox so if any of those kinds of services are in use, the automatic backup feature may added those photos to his photo archive and they might have to be deleted there as well. (If any backup/sync solution is setup to 'sync' it should delete those targeted photos once you delete them off that Tab but that's not an absolute. Some of those services are just for backing up files, some do backup and syncing but can be set to only do backups.)