Ftaher of my 2 children has not contacted them since May and has not seen them since 11/2014 now he is trying to get custody

You do not state that you have any orders addressing custody or parent-time. Based on that assumption, yes, dad can seek custody and fight for custody. You really need to get with an experienced family law attorney and take this matter very seriously. If you do have custody orders, then you need to review those orders with an experienced family law attorney to see what your rights and options are. Just because the children have been with you, and the facts you cite, those are no direct reason why he could not gain custody. It is a dangerous area, where you could get into deep trouble. You need to associate with an experienced family law attorney you feel comfortable working with. I have, and am, handling cases similar to yours, and I am open to accept new clients should you be interested.