100, when compared to 5 year old boys.
It depends on the size of the boy since all 5 year old boys grow at their own paces.
NO
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Most 15 year-old boys are fertile.
Yes, it is normal for a 5 year old to get erections during the day. It is even normal for baby boys and toddlers to get erections.
There are not many girls that dig or like 13 year old boys. They may like the boys as friends only.
they are appropriate for 9 year old boys
Yes, it should be hyphenated like so: sixteen-year-old boys.
No, girls are intrinsically cooler than boys.
Because Boys are mean.
That is not 'normal' in the sense that most 5-year-old boys don't do it. The problem is, "Where did this 5-year-old" see or hear about kissing penises?" He may try other things that could turn out to be more harmful.