If people discern, with the help of a pastor or lay pastoral worker that an irregular incestous union is the best they are being called to in the concrete circumstances of their complex situation, who are we to deny Communion to a brother and sister living as husband and wife who sincerely want to change their situation? They might need to continue their relationship...you know, for the kids. All incestuous situations are unique. We can't pigeonhole or engage in overly rigid classifications.  Rule books are so yesterday!