Mariah Yeater''s ex-boyfriend says he is certain that he is the daddy of the baby she claims Justin fathered and wants to take a DNA test to prove it.

TMZ had alleged that Mariah Yeater had sent text messages to a friend fingering her ex, Robbie Powell, as the baby daddy.

Sources close to Powell claim that he's making his move because he's tired of Yeater using the kid for media attention.

Sources allege Robbie has been telling friends that Mariah told him the whole Bieber story was cooked-up. He believes she did it for the money because she's desperate for cash.

According to sources, Powell has been approached by several media outlets to tell his story and he's reviewing his options.