If you are being sued by someone who was not a party to (involved in) the other lawsuit, then yes, you can can potentially be sued--persons not a party to a lawsuit are not necessarily precluded from bringing legal claims in a different proceeding. There are some rules about when a person *should* have been made a party to an earlier or different lawsuit, and so there are some situations where this person may therefore (if they should have been part of the other lawsuit) be barred from suing you--but it's not a given or automatic that they will be. You should consult with an attorney about your situation.