Roles of the sister in Chinese culture
Sisters are viewed as rather temporary in the home in their older years.
While the sons share the existing wealth of the family among themselves on the death of their parents, their sisters were only entitled to a dowry which they received when married as their inheritance.
A sister and a woman rarely tied to the home she was born in when they were married. Sisters were never permitted to marry anyone else that had the same surname as they did as such as person was seen as a relative and the union therefore incestuous.
However, marriage to relatives from the mothers side was seen as quite usual and so therefore, rather frequent.