When it comes to sex, there is no such thing as a “consenting child”. Age of consent is written into law for a reason.
Now various venues may determine that the age of consent occurs at different significant events in life, and it does, but the rules and case law that have built up around what is appropriate and what is not have been based pretty much on some amorphous definition of “maturity”, which means different things to different people. Is the age upon which the child may be capable of reproduction? Not all people are able to reproduce, some never will. It is the age at which the child may declare “emancipation”? Again, there are several things that argue the child is not fully mature in many ways.
A child of three years, or ten, or even sixteen, does not yet have enough life experience to give informed consent.
Precocious does not equal mature.
A child of three years, or ten, or even sixteen, does not yet have enough life experience to give informed consent.
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I’ll buy the first two age groups, but a person can get married in Alabama at 16 with parental consent (and if they have been emancipated). There may be a few other hoops they have to jump through.
Here in Georgia it used to be 16 with parental consent, but now it’s up to 17.