Ukrainian immigration of my fiancé and two children with marriage and children adoption

My dear fiancé is a nurse and has two wonderful children who were abandoned by their chemical dependent father. There appears that be a law Ukraine that even if in divorce with sole custody of the children, even these fathers are given the right of denying his children to leave the country. Obviously he told her no but still filed the paperwork with his command unit. He has been deployed but I doubt he will survive or leave awol based on his sociopathic chemical dependency issues. Please help me get her and my future children out of there including an initial green card based on the need of nursing after the pandemic has reduced the medical support for our clinical care.