Wait,I just noticed something.In that picture with all the siblings/adopted siblings...Don't they all look a little sad?Maybe-just maybe-that's the third route.
It's likely that the picture in question occurs just before you make the decision to side with either/neither faction. It sorta looks like they zoomed in on the faces momentarily after these shots occured in the cutscene.
As far as I know, we know absolutely nothing about the 3rd route, except that we will not be affiliated with the two main factions, and it will be DLC after the rest of the game is released. As a result, I don't think we can do much to speculate on what we'll actually be doing or what will happen in it, especially considering we have such thin details on the campaigns we actually know about.