S.S. Gill is the legal owner or the firm and trademark Gill Sir in India. There are other people who are using the name Gill Sir in spite of the fact that they do not have the right to do so in the field of education.
You find ample example of this on the YouTube and Quora. These people have been officially told not to do so.
The legal name of the entity is Gill Sir and S.S. Gill has registered it as a trademark in India and it cannot be used by other people. Any other people who are trying to it will soon have to pay fine for it if a court case is started.