“My mother would like to obtain custody of my deceased sister’s daughter. The father has not been present in my niece’s life for no more than 4 months total (which was right after my sister passed) and she’s now approaching 16. We do not know his whereabouts and have no way of contacting him. My mother has been her primary caregiver since my sister’s death. However, she has no documentation showing that she is my niece’s legal guardian and often run into problems (i.e., school, medical, etc.). My question is, “is it possible for my mother to obtain custody or some form of legal guardianship without involving the father?” If possible, by what means?”

Most states require parental consent to adoption or guardianship. Most states also have an abandonement exception to the consent requirement. In California, where I practice, the guardianship papers are filed in probate court, and the potential guardian might be able to represent their own interests without an attorney. See if you can find a do-it-yourself book for your state, or consult an attorney. Based on the facts you give, it sounds like your mother may be able to accomplish her goal.