( CNN ) -- One recent afternoon , Brianda Cabrera was helping her younger sister , Diana , with her math homework . Brianda , 23 , is not only the eldest of three siblings , but for the past nine years she has also been their parent . The Cabreras , including Brianda , Diana , 15 and Jose , 18 , are orphans . `` My parents are gone . For me , this is the only family I have left , '' Brianda said from their home in Sandy Springs , Georgia . Their father , Rafael Cabrera , died 13 years ago in Mexico . Unable to find a job in her home country to support her children , their mother , Alejandra Medrano , decided to move the family to the United States , where she had a sister living in Atlanta . But Medrano was struck by a car and killed in February 2005 . She was 36 years old and Brianda was 14 . The children went to live at their aunt 's home , but the situation was less than ideal . `` It was chaotic , '' Brianda says . `` They had four kids of their own and it was three of us . A couple supporting all those kids ... it was very stressful for them . '' Brianda began taking odd jobs to support the family . As soon as she turned 18 , she decided to move out of her aunt 's house with her two siblings . She became a parent and breadwinner even though she was barely making enough money to pay for food , rent and school . `` She 's become a second mother and she took on responsibilities she did n't need to , to take care of us , '' Diana says through tears . In addition to living alone and being barely able to survive on what Brianda made , the Cabreras also faced another challenge : they were undocumented . Under the law , the Cabreras fell into a category known as `` unaccompanied minors , '' meaning undocumented immigrant children who have no parents or guardians in the United States . The number of unaccompanied minors in the country has tripled in the past five years , government statistics show . Last year , the U.S. Border Patrol took more than 24,481 into custody , compared with 8,041 in 2008 . The vast majority in 2012 came from Mexico ( 13,974 ) , but some came from places as far away as India ( 23 ) , China ( 16 ) and Romania ( 16 ) . Immigration attorney Jessica Daman says these statistics , compiled by the Border Patrol , may be only a fraction of the total . `` Obviously , that 's just the children who are apprehended crossing the border ; new arrivals in theory , so nationwide , who knows how many we have that were n't undetected , that crossed without detention ? '' Daman , who works at Atlanta 's Latin American Association , took the case of the Cabreras to court . `` We asked that the children be found deprived , under state law , and that she ( Brianda ) be named their guardian . With that order the youngest two children were eligible to apply for special immigrant juvenile status and a green card . '' But what happens to children of undocumented immigrants when their parents or legal guardians die or are somehow missing or unavailable to care for their children ? What happens to unaccompanied minors who enter the country illegally and get caught by immigration authorities ? The Customs and Border Protection agency , under the Department of Homeland Security , turns these children over to the custody of the Department of Health and Human Services within 48 hours of their detention . Through the Administration for Children and Families , DHHS cares for the children through a network of providers that offer foster care , group homes , shelters and residential treatment centers . The average stay in the system is 45 days and , according to DHHS , 88 % of children are released to relatives already living in the United States . For now , the Cabreras can stay together . Brianda is focusing on the younger siblings ' welfare and making sure they stay in school and take advantage of the opportunities this country offers . `` She 's going to school and I know she expects us to go to school and she 's made that possible by doing all these legal things , '' Diana says . Brianda is majoring in accounting at Kennesaw State University and working at an accountant 's office to support her siblings . `` Family comes first , so that 's the way I was raised that before anything else you have to take care of your family , '' she says . `` So I think that was the main thing . Now that my parents are gone I have to take care of my family because that 's the only thing I have left . '' The fight is not over . Brianda 's fate depends on a bill for young immigrants known as `` the Dream Act . '' But the legislation , officially known as Development , Relief , and Education for Alien Minors , has failed to pass multiple times in Congress . Brianda , however , says she wants to stay `` positive . '' That 's the only hope she has of keeping the family together . And she 's embracing that hope .
Most undocumented immigrant children without parents in the U.S. came from Mexico . The official figure may represent just a fraction of the total number . When young , such children organized into a number of gangs .