Moore was married to Kutcher, 36, for an eight year period, but decided to end the relationship back in 2011.
Now, however she's said to be keen to support him and his new love when Kunis gives birth to their first child together, reported Radar online.
"Demi has offered to help in any way that she can with the baby and with Mila. Things have settled down a lot, and she wants to be there for Ashton's family," a source said.
"She ultimately has great love for Ashton and has accepted the fact that he is in love Mila and that they are starting a family," the source added.
Kutcher and Kunis began dating in 2012, and got engaged this February.