was Grandparents' Day in the United States, a day set aside to honor the special role grandparents play in the lives of American families. That role can be a central one. The U.S. Census Bureau says nearly 2.5 million grandparents are primary caregivers for their grandchildren. To their grandchildren, they're just Mom and Dad.

James Moeller is a typical 7-year-old boy. He loves to go biking with the man who has helped raise him since he was born. "I don't have a dad. I just call my granddad dad," says James. 

James does have a mother, whom he sees now and then and even calls "Mom" when she's there, but they aren't especially close.

"I don't hug her because she smokes. I don't like it," James says

His grandmother, who has helped raise him since he was born, says when her daughter visits, she doesn't see "that mother-son (relationship) coming out."

Marie Moeller says her daughter gave birth to James when she was sixteen and "seemed to bond with him in the beginning. She would hold him and give him his bottles at night. Then at four months she just left one night."

Ever since then, Marie and her husband, Bob, have been raising their daughter's son as their own child. 

"We had hoped that Amanda would turn around and take care of him," Bob Moeller says, "but it just hasn't happened over the past seven years."

Marie says she and Bob "are trying to do the best for him, but he seems to demand a lot of time and our attention."

The U.S. Census Bureau says there are more than 6.5 million children like James who are being raised by grandparents or other relatives instead of by their parents. That number is small compared to some nations in which nearly an entire generation has been lost to AIDS, but it is growing.

"There are more than 200,000 new children that are being cared for by grandparents since the last census," says Donna Butts, executive director of the not-for-profit organization Generations United, which works to improve the lives of the elderly and the young in the United States.

Butts says there are many reasons grandparents in this country take over as primary caregivers. "You could look at any societal ill, but the number one reason is substance abuse, and the fallout from substance abuse."

Teria Drayton agrees that substance abuse is often the reason parents can't take care of their own children. She hosts a grandparents' support meeting twice a month in Washington, D.C. 

"I just wish that parents would step up sometimes, so they could relax and do the things they are supposed to do as grandparents," Drayton says, "like vacationing or even just sitting at home all day and do nothing."

The grandparents who attend her meetings also think about missed vacations sometimes, but they don't express regret at keeping the children in the family.

"They (the children) need to be with their grandparents. They really don't need to be with somebody else," says Carol Moore, who has had custody of her great-granddaughter Michea since she was six.

I'm 66 and she is 13. I'm not young, where I can get around like I used to, but I'm able to do things that I need to have done for her," Moore says. "I just decided that I'd go through with it and whatever it is, I'd do what I have to do to make things better for her." 

Jessie Coleman is doing the same for a 9-year-old grandson and her niece's 8-month-old twins. She says she didn't plan to still be raising children -- let alone babies -- at age 55. But she doesn't dwell on what her life would have been like without the responsibility.

"Family means more than anything to me," Coleman says. I figure all of the grandmothers out there see what their grandbabies are going through, (and) scoop them up. Give them a chance, because they need somebody to love them. They didn't ask to come here." 

Bob Moeller agrees. He adds raising James isn't always hard work. "It has its ups and downs. It's fun to have a kid to play with again, but it's a lot of responsibility, too"

A responsibility that more and more American grandparents are taking on.