Settling estate

If the house is titled in the name of you, your sister, and your step-brother, not in the name of either of your parents, their deaths should not affect any of your rights relating to the house.  Your rights depend on many factors, however, including (a) if there are any agreements between  you as to the house and/or the division of income or sales proceeds from it; (b) in what capacity title is held - are you all joint tenants, tenants in common, do you all own equal shares, or is title  held in a more complicated fashion; (c) whether there are any liens against the house or any creditors or third parties who claim in interest in the house; and, very rarely, (d) whether any of the titled owners are not, or someone claims that they are not, the true beneficial owners, i.e. that they held title as a nominee for someone else.  Also, what rights are you talking about - rights to live in the house, rights to share in the income or sale proceeds in the house, rights to decide what to do with the house, rights to evict the other title owners and/or to charge them rent for living in the hosue, etc.