Surely I have misread your post...? Both of your children - your DS and your DD - are fathered by your ex? He is the biological parent of both of them? But he only wants to see your DS? Good grief, I hope I have misunderstood. I can only imagine the damage that situation will do to your daughters sense of self worth. Do as everyone else has suggested, get some good legal advice. A man who has no interest in one of his children but fights for the other deserves neither of them in my opinion.