Watch a preview of the CBS News documentary “The Faces of Family Separation” in the video player above. The full documentary premieres on CBSN at 8 p.m., 11 p.m. and 2 a.m. ET.

America’s southern border has long been a place of controversy and passionate political debate, a 1,933 mile stretch of cities and towns, rivers and desert, snaking from California to the Gulf Coast of Texas.

The issue of immigration at the and fearful of returning to their own countries. Under previous administrations, it was up to prosecutors in border states to charge people for .

Like Susana, . “We’re going to keep the families together. I didn’t like the sight, or the feeling of families being separated,” said the president.

This seemed to end family separation as official policy. Yet since then, hundreds more children have been separated from their parents, and still more have been separated from other relatives – aunts, uncles, grandparents and siblings.

Junior, 21, has taken care of his 8-year-old brother Andy since Andy was 3. He stepped in when their mother abandoned them. “I was like a father to him. I’m the only person he’s got,” said Junior. The two were inseparable. But when they crossed into the United States, border and immigration officers did not consider Junior as Andy’s legal guardian since he wasn’t Andy’s parent. “I asked them to please not separate us,” said Junior, but his brother was taken away, sobbing. Andy was sent 2,000 miles away to a shelter in New York City.

After months of not knowing if they would never see their loved ones again, these four families were eventually reunited. The reunions are full of emotion — joy, of course, but also pain. Even in her mother’s warm embrace, Litzy asks her: “Do you love me?”

“For a child the most terrifying thing in the world is to be separated from their parent. It’s the worst thing that a child can experience,” says Dr. Cristina Muñiz de la Peña, a New York psychologist who specializes in caring for immigrant children. “These children and parents are in a constant state of alertness, in hypervigilance, because they are not safe still. We’re not secure. We’re not settled.”

As they await their asylum court dates, the families struggle to cope with the possibility of deportation back to the dangers they say they fought so hard to escape — and yearn to make the United States their new home.