iPad showing music from son's purchases - want to remove

Hi,

At one point my son had no access to a computer, so he logged in to my laptop and synced his iPod here. I do not remember what I had done then, but all his music purchases come into my iPad. When I go to music I had unchecked a whole bunch of songs I just didn't want, but many others keep showing up on my iPad. I wouldn't mind if it was music I would listen to, but it's not. How do I remove those purchased songs out of my iPad. I only want my purchased songs. I sync usually with iTunes and click through playlists I make.