Feminism is surely related, but I’m not sure if it is a cause or a consequence (or maybe both?) to the decline of family.
An important factor to consider is the nature and place of work: Men used to inherit their families business or work in the same town. Big families and relatives lived close to each other, so women could use help from other women in the family for child rearing and house chores. Nowadays you have to move to capitals/big cities to find work which deprived women from the assistance they found in extended families. I think this had an impact on gender roles and the increase of feminism and nuclear families.
> Men used to inherit their families business or work in the same town.
Few men got to inherit a business but if your father worked a trade then you would probably find going into that trade to be a natural path. The latter part is still very true today.
An important factor to consider is the nature and place of work: Men used to inherit their families business or work in the same town. Big families and relatives lived close to each other, so women could use help from other women in the family for child rearing and house chores. Nowadays you have to move to capitals/big cities to find work which deprived women from the assistance they found in extended families. I think this had an impact on gender roles and the increase of feminism and nuclear families.