No, it is not halal to marry your sister in Islam.
According to Islamic principles, marriage between blood relatives is strictly forbidden (Haram). The reference clearly states: " No, they cannot Marry , this is one of the basic principle, of Islam that marriage in blood relations is Haram, and one who consider it as permitted is not a Muslim." Therefore, marrying a sister falls under this prohibition. Anyone who considers such a union permissible is considered to be outside the bounds of Islam, according to this source.
