Sister Niece
A sister niece is the daughter of one's sibling, who is also considered to be their niece. This relationship is formed when one's sibling has a daughter, making the niece both a niece and a sister in relation to the person.
A sister niece is the daughter of one's sibling, who is also considered to be their niece. This relationship is formed when one's sibling has a daughter, making the niece both a niece and a sister in relation to the person.