If you’re already a resident in Qatar and would like to get a member of your family for a visit, all you have to do is visit the Ministry of Interior website (click here) ; and then go to the MOI Forms section and download the “ENTRY VISA/EXTENSION APPLICATION” PDF and fill in the required information.
The visa is usually valid for 30 days, and can be extended by resubmitting the same form.
Requirements for applying visa for wife & Children:-
1, copy of personal id or passport of the resident husband
2, Letter from husband's employer citing profession and salary
3, copy of attested marriage & child birth certificate
4, copy of wife valid passport
5,  Bank Statements (stamped) for minimum of 6 months ( I'm not sure)
6, Residential tenancy contract (Its's depends)
For attestation & translation please contact sheen services as they are the best in Qatar who is very flexible, reliable with competitive price.http://sheenservices.com/contact-us.html