I seriously doubt that laws banning incest between consenting adults would hold up to a court challenge. It certainly doesn't make much sense in light of the sodomy rulings.
Personally, I couldn't give a crap less if a brother/sister father/daughter son/mother or whatever wants to sleep with each other as long as they don't ask for any special favors for it.
Editorial: Trying To Outrun Lawrence (Its Time Liberals Legalize Incest Alert - Don't Be Hypocrites!) (Townhall.com 08/28/05 - Jeff Jacoby) - ages 45 and 30.
Alabama Brother, Sister Arrested for Incest (AOL news 4/22/05) - ages 44 and 41.
New Book Surveys Rape/Incest Victims and Abortions (Source: Elliot Institute Published: 6/28/2000 )