my sister has been living in the house my parents bought for about 20yrs since thier death. Is there away to make her sell the and split the proceeds

If the title is still in the name of your parents, was there a will? If not, someone needs to become administrator to sell the house by an estate.

Interesting question. I assume there was either a will that left the house to all the siblings equally, or no will but by law the house passed to all of you.  Either way, you can bring an action in Supreme Court for partition of the property, which would entail a judicial sale, but it's unclear whether you'd win, given the passage of time. If you and your siblings have contributed to the cost of upkeep on the house, taxes, mortgage, maintenance, repair, and treated the property as your own, and your sister as a tenant, you have a chance of succeeeding. In that case, an alternative to a judicial sale would be for your sister to buy out the three of you if she wishes to stay in the house.  If on the other hand your sister has handled all of the costs for the past 20 years, it's likely that the court would determine the the house was divested by the fiduciary (assuming someone was appointed administator or executor), meaning at a certain point it was no longer part of the estate and it didn't pass to you by law. If there is an actual deed to the property that names all of you, that would help prove ownership.