Monthly Visit Visa for family

Iam planning to bring my family for one month visit visa,i want information about the documents required,i know marriage certificate is a must duly attested and notary done to be submitted and wife and childrens passport copies and childrens birth certificate require,but somebody told me childrens birth certificates also needs to be attested,whereas I have two sons aged 15 & 19 respectively does it necessary to get their birth certificates attested from the embassy to or their Passport copy will suffice to apply for their visit visa application consideration.please clarify this issue at earliest so that I could apply for the same without any hindrance. My email id is [email protected] thanks and best regards to Qatar living family and friends