What are the most difficult challenges a step parent faces in gaining the trust of their new children? Do share.

Never give the kids the impression that you are trying to replace their parent. I feel some step parents try so hard to step in as replacements which is an ideal but it is not realistic at all. You are a parent but not the parent (does that make sense). Give it time, be patient and let things happen naturally. Don't force yourself into the child's life, you'll only end up pushing him or her further away.