something.rb

# Fetches the responses and uses the first N elements of the array 
# where N is the same number of associated_objects the parent object has.
def responses_and_associated_objects
  # response is hard-coded for demonstration purposes
  response = {"something":[123,456,789,101112,0,0,0,0,0,0,0,0]}
  # this next line is ugly, thoughts?
  response['something'][0..associated_objects.count-1]
end

Maybe this?

associated_objects.map.with_index{|associated_object, index| response['something'][index]}