Responsibility of taking care of a woman

Q: A man was taking care of his sisters (due to both parents passing away years back). He has now passed away, amongst his descendants there are 6 kids and a wife, of which only 1 baligh son aged 17.

The sister has 4 paternal uncles (papa's) and 3 maternal uncles (mamajees) and a sister. She is not fully mentally okay and needs someone to oversee her daily living.