My15 year old son currently lives with his dad and dads girlfriend and her kids. I found out my son is dating and possibly having sex with one of the girlfriends kids. Can I make him come home with filing for emergency custody?

You can't make your son do anything. If there is a court order in place and him living with you would violate it, you have to petition the court to change the current custody agreement. I don't know if this would qualify for an emergency change in custody. Does his father know about the situation? How did you find out?

If there is no custody order in place, and his father has been legally established as the father, you can't just go and take him either, as the father would have as much right to have custody as you do, and absent a court order, police won't intervene to remove your son. To be able to help you further, we would really need to know what the current custody arrangement is, and where you are located, in addition to the questions I asked you earlier.

There is no court order either way. Me and his dad are separated not divorced. My son went to live with him. The situation were he is dating where he lives is not good! And yes his dad knows.

No good dating is very subjective and will probably not be enough. But since there are no court orders, what you need to do is petition for primary custody.

Right, go to Court and ask for custody. The Court MAY require you to prove that your son is in physical, mental, some other danger.

Have you talked directly to your son and his father?