@cimberlee,
I still think the guy's a jerk. Sugarcoat it all you please - real fathers publicly acknowledge their children. He's sweeping you under the rug and pretending that the brother is the father. The brother isn't manning up, either. He's complicit in the lie. And they're trying to keep you quiet, too.
Yes, he wants his ex. And she's really being the only person at all upstanding in any of this, and is telling him to hit the bricks. Yet he is persisting.
I do hope you've got a child support agreement in place, although I will bet serious coin that you don't. This loser does not want to be with you - he wants out, and he's bothering this other woman who is telling him to shove off, and getting his brother to lie about the child.
You still want this jerk in your life? You still want to devote your romantic notions and time to him?
Do your kid a favor. Get a child support agreement. Have it backed by a court, so that you can sue this guy's ass when he defaults and skips town. Because I can see in my crystal ball that that is a very real possibility. Regardless of your feelings or your self-esteem or lack thereof, your child didn't ask to be brought into this drama.