My husband has physical custody of his 2 children, aged 3 and 5, from a previous marriage even though custody is considered joint. Their biological mother has been living in Wisconsin for over a year now. About 2 months ago we received a call from her family saying she had moved to Pennsylvania but could not be found. She will not even admit to us that she has relocated at all. She calls the children from time to time and they always seem upset and confused afterward. The situation has become more and more stressful for the children and we would like to be able to give them a more stable life. She has not seen them in almost a year, she has never paid any child support, and we now have no way to find her or even just an address for her. At this point is there any basis for abandonment or ending her custody rights?