My wife who is under my sponsorship can sponsor her mother/sister ?

Your mother-in-law and sister-in-law can get visit visa under your sponsorship by submitting your, your wives and the inlaws passport copies to prove the relationship.

I don't think she can sponsor anyone since she is only a dependent of her husband but the husband can sponsor them.

Thanks for all your inputs,more info-she is working for a small school which does not take responsiblity of sponsorship.

-atef can you please tell me what is the procedure ?

Regards.

No. People who are sponsored by other people (not work) cannot sponsor anybody else.

No she cant cause she is under your sponser ship , but u can sponsor them under your name

yes she can

No.