Complex sentence: It is the responsibility of the women's maternal uncle to ensure that each marriageable woman in the family has a room of her own and to this end will build either a new house or more commonly additionally annexes to the original one.
Split into simpler sentences: It is the responsibility of the women's maternal uncle to ensure that each marriageable woman in the family has a room of her own. To this end he will build either a new house or, more commonly, annexes to the original one.