The introduction of a step-parent into a family due to various reasons e.g. death of one spouse or divorce, can cause be a source of arguments and if not checked can lead to young people moving out to become first time tenants. Learning to live with a new parent (whether its a step-dad or step-mom), and possibly also new sisters and brothers, take a lot of adjustment and psychological re-positioning.
The new step-parent may have different ideas about how the people should lives, and they may expect you to keep to their rules. Accepting this can be difficult, but especially if you feel that your step-parent has no right to tell you what to do.
If one of your parents has died and a step-parent comes on the scene, it can be especially hard to accept that new person into your family.
It is at this juncture that one may be tempted to ask themselves whether the step-parent are the new tenants in their house, a guest or he or she is one of them. One might feel resentful if it appears that your step-parent is trying to fill the shoes of your mother or father. Try to remember that your stepparent probably isn't trying to replace your mother or father. It is possible that you probably want to support you but don't know how.
Whatever your situation is, there's no one-pill cures all - but talking things through and agreeing on ground rules together can really help. Negotiate calmly, be prepared to compromise, and don't force your 'real' parent into taking sides with you against your stepparent, as this will only cause more trouble.