I am seeking advice about the process of transferring guardianship. I am the legal guardian of my 15 year old sibling. I had to remove my sister from foster care due to neglect of care from my mother who has a genetic neurological illness. The illness advances in middle age and worsens as one gets older. She is unable to properly care for my sister. At the time I felt guardianship of my sister was the best choice. My mother kept my sister from having a relationship with our father because she has for years been bitter about their divorce. So at the time we felt my sister would be most comftarble living with me and my wife and my father had no objection to the decision. The judge ruled in our favor. My sister is now bonding more with our father during visits and phone calls and we are starting to think it is best that she stays with him. He always wanted to be a part of her life and we have a growing family and we know that he can provide the maximum care and attention she needs. So my question is what is the process we would have to go through to give guardianship of my sister to my father?

Was his parental authority removed at the hearing or does he still have a legal part in the child's life? The answer to that will help in answering your question.

Go back to the same court (preferably the same judge) and ask that guardianship be transferred over.

However, if his rights remain, you can probably just have your sister move in.