I've having a bit of a slow night, so have a few general headcanons for Lucifer and his siblings.
Of the original six angels, the Speaker is the oldest, followed by Michael, Lucifer, Raphael, Gabriel, and finally Uriel. The rest of the high seraphim, cherubs, and other subspecies were created later, just before Earth's formation.
The original six were God's first creations, and thus have the strongest connection to Him. The more God created, the less of grace He used, leading to increasingly weaker angels.
Not including the Speaker, Michael is the tallest, with Gabriel coming in at a close second. And, surprisingly enough, Lucifer ISN'T the shortest. That title belongs to Uriel, who is about an inch shorter than he is.
While Lucifer was the closest to Michael growing up, he held a special soft spot for Gabriel and Uriel, as they were the "babies" of the family.
When the time came to exile Lucifer, the combined might of all the high seraphim wasn't enough to force him out of Heaven (as we saw, a blast from his magic ALONE is strong enough to break through their force field). As such, Michael was given the painful task of casting him out, as only he and the Speaker exceeded Lucifer's strength.
