To any woman just starting out as a stepmother: do this with your whole heart, and with no real expectations. Those two things can live together — I promise you they can.
But please, make sure you are actually welcomed and accepted into that role before you step into it. Have extremely open, honest communication before you jump in — not after. Meet the children. Feel them out. Meet their mother, even if it’s just a light introduction — it tells you more than you’d think.
Don’t go into it blindly, believing it will work itself out. Often, it only works itself out if the people around you are actually willing to let it.
You can give everything you have and still need the door to be open from the other side. Check for the door first. Then give everything you have.