ABC News' Tom Shine and Amy Bingham report:

The congressional hearing room in the Rayburn House Office Building was lit brightly, all warm and cozy. The chairs around the witness table were comfortable, and a bottle of water was set before each place.

 It was quite a contrast to  the living conditions  of Rumi Khan,  an 11-year-old sixth-grader; Brooklyn Pastor, a 12-year-old seventh-grader;  and Brittany Amber Koon, a Pvt. First Class in the U.S. Army .

Bounced between motels and homeless shelters, sleeping in cars, using gas station bathrooms to wash up and brush their teeth in, these young people were here to ask a Congress -47 percent of whose  members have a net worth of $1 million or more - for a little help.

Koon, who said she first became homeless in eighth grade, had been in and out of foster care, slept in her car and "couch surfed." When she leaves the Fort  Hood base  for the holidays, she said she would still have no place to call home.

"Like me, you have chosen to serve your country," she told House Financial Services Subcommittee members.  "You here in Washington, and me in the field.  Just as you have faith that I will be out there protecting you, it is my hope that you will use your power here to protect youth like me."

Koon was one of six to testify before the congressional committee.  According to a recent report from the National Center on Family Homelessness, one out of every 45 children younger than 18  in the United States is without a home. As a result of the recent economic downturn, almost 500,000 more children were pushed into homelessness, an increase of 38 percent.

"This is a national embarrassment that we have children on the street, that we have veterans on the street," Rep. Michael Capuano, D- Mass., said at the hearing. "It doesn't speak well for us as a society."

As the law currently stands, Koon, Pastor, Khan and their families did not fall under the definition of "homeless" while they bounced from couch to car to motel room, and were therefore not eligible for federal housing assistance.

Congress is trying to change that by expanding the definition of "homeless" to include people who "double up" on the couches of friends or family, sleep in emergency hotel rooms and spend nights in their cars.

"The importance of having a home cannot be overemphasized," said Kansas City, Mo., Mayor Sly James on  a conference call with reporters. "Stable housing is a platform from which people build their very lives."

Homelessness is on the rise in 42 percent of the 29 major U.S. cities surveyed in the U.S. Conference of Mayors report, with the average city seeing a 6 percent increase in its homeless population from 2009 to 2010. In 64 percent of those cities, officials expect that number to continue to rise over the next year.

"This should be a wake-up call for all the cities involved," James said. "Here in the richest country of the world we have people who cannot find a place to live and we are failing to address it so that the numbers are increasing and not decreasing. We should be ashamed of ourselves."