A cheating scandal threatens to destroy Ashton Kutcher’s new bliss with baby mama Mila Kunis!

After the celebrity couple became parents of baby girl Wyatt on Sept. 30, The National ENQUIRER learned exclusively that Ashton’s twin brother, Michael, two-timed his then-fiancée with a married woman who has since slapped Michael with a restraining order!

Mila and Ashton attended Michael’s wedding to Katie Hightower on Feb. 1, but the union is already kaput.

Katie told The ENQUIRER: “I left Michael in July. After we were married I found out some stuff that I couldn’t live with, so I filed for divorce.”

Michael, who lives in Cedar Rapids, Iowa, cheated with a married mom from Indiana. “The woman called off the relationship, but Michael didn’t want to end it,” said a family friend.

“He stalked her to the point where she was so frightened that she got an order against him.

“I don’t think Ashton’s aware of the restraining order,” added the source. “When he finds out, he’s going to hit the roof!”