Cate Edwards: Sister-Turned-Surrogate Mom

April 2, 2007 — -- If Elizabeth Edwards' condition worsens, the greatest impact could be felt by her oldest child, Cate, who would bear the responsibility of helping to raise her younger siblings.

In an interview with ABC News' Cynthia McFadden, Edwards expresses her confidence that Cate, a 25-year-old student at Harvard Law School, would step in to help take care of 6-year-old Emma Claire and 8-year-old Jack should her mother's health take a turn for the worse.

"And I've lived long enough to have this splendid daughter who cannot only protect herself, but I think can help John to protect the younger ones," says Edwards, who has prepared her children for the possibility of her death.

Already, Cate has stepped in to take on new responsibilities, helping out on the campaign trail and at home, says Edwards.

And she has plenty of experience helping the family cope with loss. When her brother, Wade, died in a car accident in 1996, Cate helped ease her parents' grief, according to her mother.

But the responsibility involved in helping her father raise her brother and sister is far greater, say psychologists who specialize in family relationships. And it will inevitably hasten her own maturity and transition into adulthood.

Older children taking care of their younger siblings is common in large families, but it's exceptional for that responsibility to come due to the death of a parent.

One prominent example is Shania Twain, the country music superstar, who at 21 raised her younger siblings after her mother and father were killed in a car accident.

"It was [tough], but I didn't have a choice," Twain told the Daily Mirror in 2003. "It also helped me deal with my grief. Having all that responsibility helped me get through it."

Bill Garrison, professor of pediatrics at the University of Massachusetts Medical School, says, "It makes you grow up fast. It makes you mature faster than you would have."

The experience comes at a crucial time for Cate, who is developing her own independent identity and establishing who she is outside the family context.

"The balance is going to be on responsibility rather than messing around and having fun," says Judith A. Myers-Walls, associate professor in child development and family studies at Purdue University.

"I've been around young adults in that situation, and it can help them grow up --