The locust are too old for the Serans to have created them. Recall that when you are in Act 4 Dom says "This looks old, too old." The writers are hinting at us that we did not create them and the Locust have been down in the Earth for a long time. We disturbed their peace and serenity somehow. It seems like we're getting blamed for the Lambent invasion on the Locust turf and the Locust are now invading our turf for payback.
The Lambent are immulsion exposed Locust. That's all they really are. The sires on the other hand, are not Locust at all. They are simply humans that were being experimented on. The collectibles that you pick up in the lab explain quite a bit. For one, it explains that one of the test subjects started growing fingernails at an increased rate(think Sires) and started to grow very little hair to the point where she had almost no hair(think Sires again). The medical file says that the 15 year old girl was going through severe joint pain and the scientists were trying to find some pain killers that wouldn't interfere with the experiment.
So the queen being human is because she may have been one of the scientist or their mother, something like that? How is Marcus' dad connected to this?
There is really nothing to tell us that the queen was the creator of the Locust or the mother of the Locust. No one really knows exactly how Marcus' dad is connected to all of this, but it seems like he was either working with the Locust at one point in time OR that he experimented on Locust.