For obtaining a family visa, he has to submit the following documents :

1. Application Form, duly filled-in and signed.
2. Letter from his Company, stating his salary, allowances, etc.
3. Accommodation Agreement copy.
4. Copy of Water/Electricity bill.
5. Bank Statement for min. six months (i think even 3 months is ok).
6. Marriage Certificate, duly attested from the concered Embassy and Qatar Foreign Affairs
7. Birth Certificates (in case he wish to bring his kids), duly attested from the concered Embassy and Qatar Foreign Affairs
8. Educational Certificates, duly attested from Foreign Ministry (in his Country), then attested from Qatar Foreign Affairs.

As his salary is QR.12K, there's gud chance of getting the Visas, with little bit of luck too.

BEST OF LUCK TO YOUR COUSIN.....