I feel very sorry for my 13 year old cousin. He isn't as developed as other kids his age because of his upbringing - his parents are very problematic people and it has affected him. He doesn't have much common knowledge and usually talks a lot of crap, then you correct him and he gets upset and in a tantrum because he thinks he's right but you know he's not.
He has the mindset of an 8 year old to be honest, which wouldn't be too bad but he just hasn't developed or learned the basic things you do as a kid. It affects his behaviour too. Sad.