Research shows that people subconsciously associate us with the things we say about other people. This effect, called trait transfer, means that if you talk about how other people are selfish or annoying, others will associate you as being that way, too. So praise the people around you. Besides being a nice thing to do, your stepchildren will associate you as having the good traits you describe.
Do Small Nice Things
Do very small nice things for your stepchildren without calling attention to them or expecting a thank you. The theory of reciprocity says that when we receive a gift, we feel obligated to make a return gesture. Newsflash—your stepchildren don’t want to feel obligated to you. However, they do want to feel accepted and comfortable, and small gestures like cooking a favorite meal or going to a movie together are good for this.
I say small things specifically, because doing big things without expecting a return is hard. Even if you tell yourself that you’re bending over backwards for the good of the kids, you’ll still end up feeling resentful over time if you never get a thank you. Trust me, I know this one from experience!