That is going into the hypotheticals.
Is he going to learn if his parents let him off with the excuse
that he is still a child? How many other kids will this boy molest
and destroy their psychological well being before the law catches
up with him?
If I am a parent and he is a relative , I will want to see him
punished for the good of all. I want his parents and him to
apologise to my daughter and make her happy about justice done. I
want his parents to mete out corporal punishment on him as a
consequence of his behaviour.
If not, all the relatives with young daughters will be alerted to
watch him closely or keep their daughters away , and a police
report will be made .
12 year olds around the world committed worse crimes before. This
boy has to know clearly and damn well that what he is doing has to
stop once and for all or he will face the consequences. If he still
does not learn that his behaviour is criminally inappropriate ,
then better to give him a taste of how the system works . Scare him
into behaving. Let him have the fear of doing something criminally
wrong.