NEED SUGGESTIONS BEING A STEP MOTHER.

So my boyfriend was married and have 2 kids. We are going to get married by the end of this year probably or the beginning of new year. I don’t know if he is planning to keep the kids with us (not that I was prepared to be a step mother) I’m a model and a very ambitious person, as in i value my career the most, but I still wanna be a good step mother. So ladies, any suggestion being a step mother? How do i handle this situation.