I am leaving Oman and my visa will be cancelled. My wife has a family joining visa but she is at India. So, will her visa automatically cancel if I cancel my employment Visa without her coming back to Oman? Will there be any problem if she needs to apply for a visa in any other GCC country(Qatar or UAE) as she have the Oman family visa stamped on her passport?
Assuming your wife is on a family joining visa, the validity of her visa is tied to yours as the holder of the employment visa. If you get an exit stamp and leave the country, it should follow that her visa would no longer be valid either.
Have a look at our Visas for Oman page to get a better idea of how the system works.
She should check with her closest Omani embassy or consulate, but I don't think you'd have any problems.
Hope this works out,
Best
Xavier