iPhone photos synced to iPad

If you do not want or require your photos to be synchronised between your devices, you simply need to disable Photos in iCloud:

Settings > [Your Name / AppleID] > iCloud > Photos >

• iCloud Photos - set to OFF
• My Photo Stream - set to OFF
• Shared Albums - set to OFF

Additional information can be found here:

Set up and use iCloud Photos – Apple Support

if they are synced to icloud they are not really physically on your ipad just available on it because the 2 devices have the same appleID