I understand your anger, but after three months you are going to have to let it go. It's only going to look like it's still bothering you after all this time. It's best that you know what type of people the brother and sister are and stay away from them. If you've been away from your ex for three months and this is the only thing bothering you, consider yourself lucky. You could still be lovesick over your ex. You're mad because they are dishonest, two-faced, back-stabbers but the truth is they are in your past so leave them there and keep moving on.
Thanks for the reply. I accidentally deleted when i was trying to edit, but it nice to hear from someone else exactly what they are. My best friend keeps telling me to forgive them and move on but it''s a little hard when it's your reputation being ruined. Just hearing another person call them what they are helped a lot.