The ratio of dark matter to matter is roughly in proportions $1:5.4$
This suggests that if there were about 6 Universes placed in the same space that were completely invisible to each other, except for the gravitational force, then this is what we would expect.
Some people have said that some of the dark matter could be made of "mirror matter". But if mirror matter had the same mass and particles this would not add up. But if there were another 3-fold symmetry perhaps there could be 6 types of matter. Each type only interacting with itself.
The funny thing about these 6 Universes is that their galaxies would all roughly be in the same place. So each galaxy would in fact be 6 overlapping galaxies. (Perhaps in a nice symmetrical arrangement). (Would they all spin in the same direction?)
In each of the 6 overlapping Universes there might be lifeforms that we would never see.
So if each particle that we know of actually came in 6 types and particles could only interact with similar types then this would have to be true.
Is this possible to prove or disprove?
(I would think that in the center of the galaxy, where all 6 galaxy centers coincide there would be more gravitational interaction between "dark stars". Whereas near the arms if the 6 galaxies are not lines up there would be less interaction. Assuming galaxies are disc shapes in all 6 univereses)
Edit: Some people have pointed out that dark matter interacts less strongly. But if each of the 5 dark Universes don't interact with other 4 dark Universes, only themselves, it would mean the dark matter in total would interact precisely on fifth or $20\%$ with itself on average.