Child issues

My children have a step sister who they feel is terribly mean to them. It is to the point where one childs grades are suffering and they no longer want to go to their dad’s if she is there. Too many issues to mention. Today was the last straw. My daughter is 9, has excelled in school until this year(when they have had to be around step mom and step sister). Now I am having to put her in tutoring, she cries, cannot
concentrate in school (this is what she says) and when I talk to her about what is wrong…it always is about the step sister and how horrible she behaves toward my daughters. The other one is also upset, but one is much more upset than the other. I cannot continue this way. My ex will not deal with the issues and fluffs it off as step sister conflict. It is effecting her terribly. What can I do? We do not have a final custody in order and I have so many things stacked up against him and his poor parenting. I want them to see their father, but not like this. He refuses to take them on a day that he doesn’t have the step child. Personally, I think he doesn’t want to lose a day alone to fill it with kids. Please help!

Keep the children with you unless the other child is not with your ex. If he files for custody you can use all the evidence you have regarding how begin in his care and in the presence of his step daughter is not in your childrens’ best interest.