My son is 13 and was adopted by my sister and her husband. I live in wv and he lives in pa. we have been able to spend some quality time together lately and have done a lot of talking. My son proceeds to tell me that he does not like living with them, and there is an awful lot of favortism between his 10 year old sister and my nephew. He does not like it there and he wants to live with me. Is he old enough to make a decision or will I have a long battle in court? He wants to learn stuff but is not able to because there refuse to help him.

First, it is nice of your sister to allow you to spend time with your son.
Unfortunately, once you gave him up for adoption (if you really did a formal adoption), then in the eyes of the law he is not your son, and there is no court battle that you can even begin to hope for. And your son has no say in the matter, even if it were just a guardianship. The court would listen to his preferences but not make a determination based on them.

Keep in mind that just about all teens think some other family is better than theirs, or the parent they don't live with is preferable. It's the growing pains of teenagers. Wanting to learn stuff that they won't help with? Really, what this sounds like is a boy who doesn't quite understand what things cost, for starters. If one kid got lessons in something and he was refused lessons in something else, it could be because of both cost and the appropriateness of the course. Four things: she's your sister, she helped you out years ago, she has supported him, and she allows contact. Those are not signs of someone who shows favoritism, and is selectively hard on him.

(You said favoritism between his sister and your nephew, which is puzzling, because it implies that she adopted your daughter too? Doesn't change my response, however.)

There is nothing to decide, he was adopted, and is their son legally, not your son.

I do not even know what court battle you are talking about, this was a legal adoption and can not normally be undone.

So really I don't see anything you can do, but be happy they even allow you to see child.

As noted this hinges on whether this was a legal adoption. If so, the likelihood of it being overturned is extremely slim. And their son (not your son any longer) has no say in the matter.

If it was not a legal adoption, then a court has to decide. At 13 not much weight will be put on his preference.

I'm curious though. What "stuff" does he want to learn that he can't?