Dating someone with kids means their children come first. Always. If you can't handle being second place sometimes, this isn't the relationship for you.
Don't force a relationship with the kids - let it develop naturally. And remember, their other parent will always be in the picture. How they coparent says a lot about who they are.
The Rewards
Stepparenting is hard, but it can also be incredibly rewarding. Watching someone you love become a family is pretty special.