My mother and step father were married 30 years. My mother passed away three years ago. My sister and myself never received anything. Now my stepfather is dying. My mother worked the whole time they were married and bought everything together. My step sister and step brother are saying when he passes away that we are not entitled to anything.is this correct?

Did your stepfather adopt you? Does he have a will? What state or country are you in?

In most places, yes, what you step-siblings are saying is correct, assuming several things:
1. all property was owned jointly, with right of survivorship; and
2. your step-father doesn't provide for you in his will.