User blog comment:Kajune/Lucifer, first son?/@comment-26992577-20160408122012/@comment-26992577-20160408124047

It's difficult to dinstinguish between retcon, contuinity error or the above mentioned solution.

Btw. there is another possible retcon in this statement: If Lucifer is God's first son, you can say Michael is younger than him. But you can also say they did not intend to retcon Michael's age but rather his relation to God. Maybe they wanted to tell us that Michael is not God's son but Amaras. That would still retcon the s5 arc, but anyway there is not method to decide which explanation is more plausible. So it's also speculative to call Lucifer the oldest archangel.