Rails 3 - Ancestry gem, root not is showing siblings.. Is that correct?
parent           Returns the parent of the record, nil for a root node

ruby-1.9.3-p0 :024 > c
 => #<Bin id: 56, heading: "Bin 1 Heading ", ..., updated_at: "2011-12-06 00:51:06", ancestry: nil>
ruby-1.9.3-p0 :025 > c.parent
 => nil
ruby-1.9.3-p0 :026 > c.has_siblings?
   (0.3ms)  SELECT COUNT(*) FROM "bins" WHERE "bins"."ancestry" IS NULL
 => true
ruby-1.9.3-p0 :027 > c.sibling_ids
  Bin Load (0.7ms)  SELECT id FROM "bins" WHERE "bins"."ancestry" IS NULL
 => [1, 2, 3, 4, 5, 56, 57, 58, 59, 60, 111, 112, 113, 114, 115, 166, 167, 168, 169, 170, 221, 222, 223, 224, 225, 276, 277, 278, 279, 280]

bin.parent = nil  # set as a root node