Ofcourse, your father primary sponsor unable to meet the income requirement then joint sponsor who meet the income requirement can submit Form I-864. Max is 2 joint sponsor is allowed.
If a joint sponsor is used, the petitioning sponsor must use Form I-864; he/she cannot use Form I-864EZ.
If you are capable enough to sponsor your sister you can do it alone. If you are at right age, domicile and citizenship.