Biological Preference
It sounds to me like you two have some communicating to do. First of all, I'd encourage you to focus on your wife. I think you need to take the initiative here to establish a regular time of prayer and Bible study, where you grow together spiritually and work through those adjustments. You need to ask your wife, "What can I do to communicate love to you, and how can I lead you spiritually?" Seek to get on her agenda, and love her sacrificially with the love of Christ. Then, after you've talked about meeting her needs, it might be a good idea just to help her understand what your own needs are, as well.
You need to examine your relationship with your stepson, too. For example, if you are becoming resentful of this him, your wife's going to sense this and seek to protect him.
One final thought. It could be that your stepson feels like the odd man out in this family—just the way you feel right now. So pray about it, talk to your wife about it, and seek to build a better relationship with her son.
I'm Dennis Rainey, and that's Real FamilyLife.