Jacob can eat 12 / 2 = <<12/2=6>>6 candies before crying.
Lana can eat 6 - 3 = <<6-3=3>>3 candies before crying.
Nellie, Jacob, and Lana all ate until they cried, so they ate 12 + 6 + 3 = <<12+6+3=21>>21 candies.
Thus, there are 30 - 21 = <<30-21=9>>9 candies left in the bucket.
After dividing the remaining candies equally, they will each get 9 / 3 = <<9/3=3>>3 sourball candies.
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