Should i still try to keep in contact with any of them?

So a guy's sister revealed to me his deception with dating both me and another female he was in an established relationship with. However, information leaked out that she was the one who caused me to leave him, and it caused a bit of problem. However, 2 months later both the sister and her brother put up pictures of them together as little children. And when I tried to message the sister, just to say "hi," she never did respond.