I keep 2 together in the kitchen when i go to bed ( my 2nd oldest and my very youngest, and 2 in the livingroom ( my very oldest and 2nd youngest )
I always wake up to them cuddling.
But i would never leave my second oldest with my eldest or 2nd youngest because she is very domanant over them and she has caursed fights because of this, trying to part 3 bull terriers in a fight was not easy, So the order i keep them in now is the order they get on most with, without a fight breaking out over domanants.