You can access the internet and certainly research law on incest in your state. Is it incest for half brothers to have sex? I don't know.
Legally oral sex is sex. Any sexual contact is considered "sex".
Your condition is not material in the least from a legal aspect.
Before the law becomes involved, it has to be reported to the law and there has to be evidence. I don't see anything serious happening to two minors, but you need to research Arkansas law.
Hopefully someone else will have more knowledge on this area. I just don't have the time to research it, and you can do the same.

