Kunis is said to have moved into Kutcher's Los Angeles home and the couple are discussing having children, reported Closer magazine.
"They've been so happy since moving in, they've said they've discussed starting to try for a baby. They don't see the point in waiting when they're so deeply in love and want the same thing," a source said.
The couple are deeply committed to their relationship and it is being rumoured that they will get engaged once Kutcher's divorce with Demi Moore is finalised.
"Mila knows she's not always going to be liked by Demi, but she's done nothing wrong. Now she and Ashton have decided to make a real go of things together, she's never been happier," the source added.