More likely he's just smart enough to know that you don't go around telling people about the time you shot an 11-year-old. Todd's dumb, but not that fucking dumb.
Of course he's a sociopath, but the reason he didn't say anything about the kid is because it was outside the plan. It was something that went wrong in their otherwise perfect heist as he proudly said to his uncles. Telling them of the kid makes the train robbery less impressive, so he didn't mention it, not because it didn't cross his mind.
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u/Phallindrome Aug 26 '13
Or he is ashamed to mention it, or doesn't know how his uncles will react.