User blog comment:Bharatram1/Who is stronger ? Lilith or Azazel ?/@comment-86.140.130.217-20120512221938/@comment-4920092-20120512224727

Good question. It's possible that he doesn't need permission to enter the houses, per se, but to alter the kids. It's possible that, because the parents are, for all intents and purposes, responsible for the children's souls, Azazel needs their permission in order for his demon blood to make the necessary changes to them.