It really isn't that bad for Delilah to be with Sven. He is only 3 years younger. Plus we all have demons so if we really wanted to make an excuse as to why we are immune to Promiscuity it could be from the demons. Dante didn't just resist Delilah for Katherin. He did it for himself and Delilah. He didn't want to be a one night stand for Delilah because he is a romantic. Plus he doesn't buy that Delilah wants to be alone forever and if she admitted it he would probably be more attracted to her. Plus he has interest in Katherin and he thinks she is more pure hearted and says writes what she feels more honestly. So he gets attracted to her because she knows him well from his secrets and there are no secrets from her and she is pretty just like Delilah.