What is the ruling on an orphaned girl and her sick mother living with her married sister and her husband in one home, and is it permissible for them to live alone in their home without the presence of a man to protect them, and is it permissible for the sister's husband to handle the marriage contract in the presence of men from her father's 'asabah (agnatic relatives)?

It is permissible for a woman to live with her sister and her sister's husband if there is no fear of temptation and if Islamic regulations are adhered to. However, it is preferable for her to reside alone with her sick mother to care for her. It is not permissible for her sister's husband to be her guardian for marriage unless he is one of her 'asabah (male agnates); rather, one of her paternal cousins should arrange her marriage.