Can you contact the step daughter yourself? It sounds like a good heart to heart between the two of you is in order. Getting the point across that it doesn't matter if you like each other or not - what matters is family and providing stability and security. Dividing the family up for activities such as holidays will put undue pressure on the 8 year old and isn't fair to him. The bottom line is, like it or not, you are family and respecting her father and her brother obligates her to at least try to be cordial to you out of respect for THEM, it's not even about you or how she feels about you. If you can't communicate that to her, talk to your husband about it more and see if this can't get worked through somehow.