The Star claimed that former American footballer Eric has been sleeping with his ex-wife Keri Johnson, labelling him a "two-timing cheat".
"He was still having sex with Keri after he started seeing Jessica," a source told the tabloid.
"She needs to think twice before marrying him. He's already cheated on her once he'll most likely do it again."
According to a friend close to Jessica, the comments are completely false.
"The whole thing is ridiculous. Eric is the most devoted fiancé and father," the anonymous friend told Huffington Post.
"There is not an ounce of truth to this. We will be serving them with a legal notice today. We weren't even consulted for a possible comment."
Jessica, 32, and Eric, 33, recently welcomed their baby Maxwell Drew into the world in May.
Jessica' spokesperson has said "no comment" about the cheating allegations. Stay tuned this one is likely to blow up.
In pics: 2012's most cheatworthy celebs
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