Your Qualification should reflect on the designation mentioned on your visa. So it should be Mechanical Engineer Visa on your residence Permit. I got my family visa rejected last week due to designation on my RP. I have Masters in Mech Engg, but my visa was Inspector. If you are lucky you might get family visa.Now my company is changing my visa as Engineer, which again requires 6 months statements etc time consuming.Hope this answers your question. Life is not easy in Qatar.