The 34-year-old and Kunis have been friends for over a decade after starring in 'That '70s Show' together and have been dating for the last few month, reported Showbizspy.
Kutcher recently split from his wife of six years Demi Moore but he feels ready to settle down again, even though his divorce from Moore is yet to be finalized.
"Ashton and Mila are talking marriage. He's planning to propose at Christmas. They're moving fast but neither of them has ever been so happy. Ashton wants kids and misses the security of being married," a source said.
Kutcher is even said to have met his 29-year-old girlfriend's parents. "She's moved into his place in Hollywood. Mila says Ashton is the man she has been waiting for all her life and wants nothing more than to marry him," the source added.