The mother kept 27 x 1/3 = <<27*1/3=9>>9 pieces of sweets.
So there were 27 - 9 = <<27-9=18>>18 sweets that were divided between the 3 children.
The youngest child got 8/2 = <<8/2=4>>4 sweets.
So the eldest and the youngest got a total of 8 + 4 = <<8+4=12>>12 sweets.
Therefore, the second child gets 18 - 12 = <<18-12=6>>6 sweets.
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