12-year-olds are definitely children, and are not able to make adult choices. Many 20-year-olds are barely able to make those choices.
There are many cases when right and wrong are mixed up, and cases when there is no definite line between right and wrong.
There are also cases when legal and wrong are the same, like when Rosa Park refused to follow the law. Now we think that she did the right thing, but what she did was illegal then.
You're as bad at History as you are at human rights, dolt.
Hundreds of years ago, people were seldom able to marry until around 25, because they were not able to afford a wedding or a home before then. The "jobs" they had were working on their own farms and/or the farms of the land-owners.
They also entered puberty later then than now, as the nutrition was poorer then than it is now, in general.
Giving birth as young as 12-13 increases the risk of infant mortality, birth-defects, injuries to the woman and death of women. In those third-world countries, there are villages with only old women and children, as most of the "adult" women die during child-birth.
Mutual sex? As opposed to unilateral sex or masturbation? I guess you mean consensual...
No, the child is not to blame as the child can't give informed consent and can't fathom all consequences of his/her actions.
The twenty-year-old is barely adult him- or herself, sure, but he or she IS legally an adult and is responsible for the situation.
It doesn't matter what you think, dolt. Science has shown that 12-year-olds are not mature enough to understand all consequences.
Having a family is much, much, MUCH more than just giving birth, you blithering idiot. Having a family is caring for the children, bringing them up to be productive members of society, providing a home, nutritious food, clean clothes, a stimulating environment, physical and mental training, etc. There are quiet a few 20- and 30-year-olds that don't manage to provide all this for their children.
When I was born, in 1969, my parents were 22 years old. Several older relatives said "Children can't have children!", implying that my parents were way too young to start a family. It's not hundreds of years ago, it's soon 50 years ago. But it clearly shows that you are wrong for thinking that people used to form families earlier in the past.