回复：小白兔：您好！十分感谢您的及时答复!

If you already include your brother and sister in your mother's 130, it should be no problem, just waste a few hundreds. Otherwise, contact NVC and consulate general in Guanzhou immediately. I do not think that it is big problem. You petitioned for your mother. It is your mother's decision to include your brother and sister in the application. I think that your mother just need to include your brother and sister's document along with hers in the Package 3.