Can you submit the same session proposal to two different conferences?
Normally, two different conferences with the same session topics will result in two groups of work that are different, but compliment each other.

For example, assume I run a session called "Computer Forensics" at two different conferences. We will either invite different speakers, or use peer review for submissions to the session. In either case the result will likely be two sessions with the same general topic, but very different specific topics.

If the governing associations do not want the same topics, then make the topic title more general, but still related.