Oman issued birth certificates attestation for Saudi

Greetings. 
I am an Indian Vet recently moved to Saudi Arabia from Oman. I  need to bring my family now.  My children were born in oman and they have got  oman issued birth certificates.  My family is in India and when I presented the birth certificates for Saudi embassy attestation, they deny with no proper answer but my marriage certificate alone is attested. I  submitted all necessary documents but nothing happened.  My questions are,
1) do birth certificates require Indian embassy stamp from oman? (We are already out from Oman)
2) or middle east issued certificates do not require Saudi embassy attestation?
3] what are the required formalities for oman issued birth certificates?
Please advise me.
Best regards
Dr Prabakar