This post would benefit from providing more context. Did the author make those videos on behalf of a company? Did he post them somewhere online? Was there ever

This post would benefit from providing more context. Did the author make those videos on behalf of a company? Did he post them somewhere online? Was there ever any kind of license (creative commons for instance) attached to them? My expectation is that at a minimum, Udemy would investigate the claim once it's reported to them. But you need to provide sufficient proof that you are the content owner. Just because your face is in the video is not enough, but it's a great start.