Is it permissible for a woman to greet or uncover her hair in front of her foster brother, and is it permissible for her to greet or uncover her hair in front of her foster brother's brothers, or only in front of him?

The foster brother is like a blood brother in all rulings except inheritance. The ruling concerning the siblings of a foster brother depends on knowing the foster mother: If she is the woman's mother, then the man is a brother to all of her children and her husband's children. If she is the man's mother or another woman, then the foster sister is a sister to all of her children and her husband's children.