Surprise, see New Scientist today:
"We’ve found a bunch of dwarf galaxies we thought didn’t exist."
https://www.newscientist.com/article/2154581-weve-found-a-bunch-of-dwarf-galaxies-we-thought-didnt-exist/
As a consequence of dual equal massive black holes as observed here, I suggest that the duality was created by the splitting of one larger BH by one minor BH. as observe in the Eagle nebula at a much smaller scale.
see below.