Assalalamu Alaikkum,

Along with the family visa application, you need to attach copy of below documents. I recently got my family's visit visa transferred to resident visa. These are the documents I submitted.

Copies of below docs
1. Marriage Certificate (Attested by Qatar Embassy in your country)
2. Birth Certificate of your children (Attested by Qatar Embassy in your country) (if you have children :))
3. Passport copy of you and family.
4.Your Labor contract given by company.
5. Bank statement showing 6 month salary credit (salary should be more than QR.7000 per month)
6. Letter from your company requesting visa for your family and your salary must be mentioned.
7. House rental agreement (contract)
8. Copy of Kahrama Bill

If you have all of above insha allah you must get family visa. I got it. However try your luck in case you don't have some of above documents.