Is It Obligatory To Bear The Cultural Expenses Of My Sister's Wedding?
No such things are made fard in Shariah. These are our cultural norms and should be dealt with accordingly. If you cannot afford it, you can request your parents to excuse you. It is our social responsibility to make expenses within our means and should not create unnecessary problems. But you cannot change society overnight. Now this is your sense of justice and ethics which should decide for you to see how to support your family according to the means available to you in this time of need.