Five each, two more. Six for each person, just finished eating.

And because everyone wants the same amount, everyone must take one more for the second time.

In other words, the two extra apples for the first time were used up by the "one" that each person was given "more".

So there are two children. In other words, you can have two children, one more for each child, just to finish the rest of the first time.

Two children, six apples each, so 6+6= 12.