"He talked with Mila's dad around Christmastime," a Kutcher insider tells PEOPLE. "He asked for Mark's blessing to marry her. It was important to Ashton to be respectful and traditional. This is the real thing for him and he wants to do it all right."
Kunis was first spotted wearing her simple diamond engagement ring in late February. As for wedding plans, a source says the happy couple are sorting out logistics and will most likely marry this year.
"They don't want to wait," says the source. "This relationship started on solid ground and everything is working out. They are in it for the long haul, truly."
"They are clearly very much in love, in tune with each other and so comfortable," another source said in September, prior to their engagement. "In some ways, it's like they're married already."
Kutcher, 36, and Kunis, 30, were first rumored to be dating in April 2012, and from that point the former That '70s Show costars stepped out together often, going on vacation together and exhibiting plenty of PDA.