What happens in families when the youngest child leaves home, making empty-nesters out of their parents?

An emotional stew of mixed feelings and changing roles, experts say.

For some parents, there's the welcome prospect of rekindling a marriage and finally having some time to themselves.

For others, the transition can be unsettling, as couples redefine their roles and face life without the constant distraction of kids.

"It's a milestone, the closing of an era," said Connie Horton, a psychologist, director of the counseling center at Pepperdine University and mother of a college-bound student. "You have all those dynamics — excitement, doubts — all combined in the process of letting go."

Students across Ventura County are heading off to college this month and next, adding more parents to the growing list of empty-nesters in the United States. The number of empty-nesters is expected to double nationally, from 8 million to 16 million, from 1990 to 2010, according to the Fannie Mae Foundation, a nonprofit organization focused on affordable housing.

Those empty-nesters will handle the transition in different ways, depending on their ages and the roles they've taken in raising their children.

Women who have stayed home to bring up their children might be the most affected. That's because they've spent years defining their role as mother, and now they need to redefine that role, said Cheryl Heitmann, a licensed clinical social worker, mother of three grown children and member of the Ventura County Community College District board.

"The last child is now gone, and there's the question of not being needed in the same way anymore," Heitmann said. "Their major role in life changes dramatically. They now need to redefine their role."

That's the situation facing Carol Kimura, a Moorpark mother who stayed home to raise her twin daughters. Kimura and her husband, Dave, will have an empty nest in one fell swoop when both girls leave home for college next month.

The Kimuras have been heavily involved in their daughters' education from the start, doing everything from taking forgotten lunches to school to volunteering for band boosters. Now they're facing a new stage in their life together.

"We'll miss them. We only have the two," Carol Kimura said. "Dave will go on with his work. I definitely will have to find something else to do."

The Kimuras' situation is fairly typical, Heitmann said. Some stay-at-home moms, like Kimura, might decide to volunteer, pursuing an interest they put aside when they had children. Others might find themselves looking for jobs or returning to school to pick up the skills they'll need to find work in today's market.

Whatever they do in the next stage, full-time mothers can expect to feel some grief, Heitmann said.

"There's a grieving process that goes on," she said. "It's a loss of a big part of your life."

Most couples, whether the mother works outside the home or not, also will find themselves facing more time together and figuring out how they want to spend that time.

No longer will they have the daily distractions of attending their kids' games, dealing with discipline issues or simply being surrounded by the hubbub that children inevitably bring to a home. Now it's just them.

Bonnie and Bill Lucking, whose youngest child, Alison, moved Friday into the dorms at CSU Channel Islands in Camarillo, plan to do some more traveling in their motor home now that they're empty-nesters. Bonnie also hopes to get back into genealogy.

Still, she knows she's going to miss her daughter, even though she won't be far away; the Luckings live in Ventura, and Alison plans to visit on weekends.

"I'm used to coming home from work and going to the mall with her, to a show," Bonnie said. "I think it's going to be a little harder for me."

Like the Luckings, couples might look for activities they can enjoy together, said Adina Nack, an associate professor of sociology at California Lutheran University in Thousand Oaks and the mother of a toddler. They also might want to do things on their own, or with their own friends.

"When we marry somebody, they don't necessarily fill all our needs," Nack said. "It's not fair to expect them to do the same activities you like to do. Couples can find other diversions for what the kids once provided."

Even couples excited about pursuing new diversions can expect some bumps as they adapt to their empty nest, said Pepperdine's Horton. They also can expect a range of emotions, about themselves, their roles and each other.

The key is to accept that range of feelings and find some balance between relief and grief, said Horton.

"Ambivalence is understandable," she said. "You're going to have some mixed feelings."