Most Helpful Guy
From a relationship coaches perspective, it depends on a few factors:
1) Why isn't he letting you see them? Meaning, what would he tell the court if/when he was asked why he didn't let you. Would his reason be valid to the courts? For instance (and I'm not saying you're doing this) would he try to prove that you seeing them would pose a danger to them?
2) Do you have a court appointed or personally hired child's psychologist that would/could assess and testify to the damage the lack of visitation has done to the kids?