I don't think you have standing to be awarded custody, however you should petition the probate court to obtain guardianship. There are several benefits to becoming the guardian of the minor children, basically it will save you and your family the heartache of going through DHS and child protective proceedings. Furthermore, based upon the facts laid out above you have a basis to obtain guardianship.
Hire a family law attorney to seek guardianship. One reason for such an order is that child is left with someone with no legal rights to kid. If guardianship is awarded you can generally put child on your health ins., just like your own kids.
Legal disclaimer: This answer is not intended to create an attorney-client relationship. It is meant to give the questioner some general information regarding their question and the questioner should follow up by consulting with an attorney who practice in this area of law.
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