She may try to alienate you from her kids. Job requires long hours over many years for no pay and little gratitude. If your stepchildren are old enough, they can even participate in setting up these rules. The Stepmom Success System program is for you.
Expect scant support from their father and possible enmity from their natural mother. Solution Trust him and communicate early, transparently, and empathetically. Family CNN -- If there was a job posting for a stepmother it might read: Woman needed to raise someone's else's kids who will fight you and test you and might even hate you forever.