Perhaps they will decide to work things out, go to counseling, and repair their marriage. Perhaps they will divorce. No matter what, though, that's something between them. You unfortunately got yourself involved, but only at the tail end. So please, don't feel it's your fault.
Parents really are people too.
Tell you what, after reading this, write back and tell what your thoughts are. And ask for more help muddling this through. Don't make yourself decide right away. Take a few days. G. Washington, that is.