That's just their thing, and I won't judge. Unless they try to shove it in your face or act like it's totally the greatest ship ever. Usually the people who ship Cordelia with her sons are huge fans of her and hate Yui (poor girl), thinking that it would be perfectly normal for Ayato to want to bang his mom.ironically, i'd seen few people in DL fandom especially on tumblr, ship cordelia and ayato, which on my opinion disturbing.
mother son relationship is one thing, but most eroge use siblings relationship. which is disturbing too.