children's rights ND

I was engaged to a man who had two teenage boys. He had gotten custody because of the mental and physical abuse the mother had put them through.
In July of last year I sold my house,appliances and quit my job to move to his home and take care of the children.(I also have three)
On January 10th he died in a car accident. We were not married yet, our wedding was suppose to be in March. He had given me Power of Attorney on the boys.Is that binding at all anymore?
On January 11th, his ex-wife called and said she was flying into town and kicking me and my three kids off the farm. She has managed to kick us off! Do I have a legal right to go after her for this? Do me and my kids have any rights in this?
Also, she took the boys, against there will. We do have the state working on that. Because of the abuse I know they'll be back. Do I have any legal way of obtaining these two?