Ex wife married military man-now trying to move with kids!

[CavScout]

Divorce sept '13 and ex wife now is remarried to military man wanting to move from Indiana to Kansas with kids but I don't want kids to go. I would gladly take full custody and she can move but I want my kids here. All family (both sides) live here. Son is 7, daughter is 1. I'm engaged with son due in April. I addressed to the courts that we had been together a year prior to actual divorce and fiancé has been heavily involved with my kids from that time. My ex wife claimed to be single as of the divorce but now is remarried and trying to move. What chance do I have at gaining custody and keeping my kids here?