Space Jockey - our sibling.

You guys have some good points. While reading all of your responses I thought of the following. What if the SJs were created much like us by the Engineers? Like the story of this Prometheus, the SJs follow clues left by the Engineers. There story is different, where they kill our creators. So in sorts the SJs are our siblings. They wait on LV-223 for any of their other "siblings", to take their technology or harvest.