My best friend is the second child in a family of four. Her parents paid for her younger brothers' education, bought them cars, has bailed her oldest sister out of so many financial obligations it's ridiculous... my friend, however, gets nothing. And never has. She moved out-of-state and now enjoys a peace that she never knew before.
The worst thing about people who treat others with a lack of respect and consideration is that they'll never admit it. It sounds like you're hoping if you confront your family, especially your step-father, he'll have some sort of break through, apologize, confess a realization that he's treated you and your children abominably, promise to do better, and thus, in the future, you can all be a happy family where things are fair.
But you know this is unlikely to happen. Very unlikely. People who routinely make excuses do not often come clean and suddenly decide they're going to live up to their word. And you've got to set aside any thoughts of how "if he loved you or your children as much..." because that isn't it, either. It's a relationship pattern that was established a long, long time ago - it has nothing to do with who loves who more and everything to do with the way the relationship has been allowed to progress.
You can stop all contact of the sort that has occurred, or you can decide you're going to be more assertive and show your children that "being nice" is not the same as allowing others to take you for granted, get away with disappointing you, etc.
Because it's our family, we are often willing to make lots and lots of exceptions. When you have children, though, you have to think in terms of: Is this the sort of behavior I would want my kids to put up with from their friends? Would I want my children to feel as though this is how friends treat each other? Would I want them to expect this from their future significant others?
For me, the easiest way has been to come up with a saying, or a few sayings, that I can repeat without backing down, and to remember when I approach the subject, I'm not there to argue. People like this will often try to draw you into an argument to prove that your perception is incorrect (and you're already doubting yourself so you don't need that) and they're not as bad as you seem to think.
In this instance, the next time your step-dad says he wants to do something with your children, maybe say: I am trying to raise my children to understand it's important to keep your word. Can I count on you?
Or when your kids see the other kids have things they don't: I am trying to raise my children to be able to be happy for others when good things happen to them, but when you are the source of others' good fortune, it makes it very difficult.
Roll around a few scenarios in your head, remember your children will benefit greatly in the long run, pray if you are a Christian, God doesn't ask us to be doormats. In fact, we are told to "speak the truth in love" and to confront situations like these...
All the best - and many, many kudos to you for trying!
E.
