Technically, having a conversation with a minor is not a criminal offense. However, if the topics youre discussing are sexual or you exchange sexually explicit images with them, you could be facing some serious consequences.
Is it OK for a 13 year old to talk to a 16 year old?
The question as phrased, the answer is no. It is not legal. If the 16 year old engages in any sexual conduct, they could face statutory rape charges and the parental consent assuming there was any would have no bearing on that.
Is texting a 12 year old illegal?
Its not illegal to text someone of any different age. If the content of the texts is salacious, solicits inappropriate behavior, etc then that might well be a crime.
Can your parents see your texts?
If you are part of your parents family plan or if your parents pay your phone bill, they have access to information about all of your phone activity. The contents of the message itself, whether it be photos or text, are not visible to your parents.