Melba Soza comforts her son Jose Antonio, as he arrives at the Bilbao, Spain, airport from the United States. "I was afraid you would have lost the love for your mother," she told him. "I was afraid you'd look at me like a stranger," he said. The mother was deported from the U.S. and the son is trying to get her back into the country.

MIAMI - He remembers the moment so clearly, the last time he saw his mother on American soil.

Jose Antonio Machado was merely 15, too young and powerless to stop what was happening. His mother, Melba, was dressed in an orange jumpsuit, wrists in handcuffs, being led away by an immigration officer.

When she looked back, he mouthed: "I love you." She nodded and turned away.

He speaks of her now in idealized terms. She is the petite woman he imagines hugging him when he comes home from school. The one whose cooking he misses and who, at 18, he still needs for comfort and advice.

"If we were together things would be much easier," he says. "Your mom is unconditional love."

Instead, Jose finds himself in the same situation as thousands of other young people in this country: He is the child of a parent who came to the U.S. illegally and then was deported -- while he was left behind.

"Jose is an abandoned child," a child law advocate wrote in the court papers that led to his placement in a foster home back in 2011. At least 5,100 children whose parents are either in detention, or already deported, live in foster care today, according to one estimate.

But if Jose felt abandoned, it wasn't by his mother but rather the laws of his adoptive country for sending her away.

For the past three years, he has been on a mission: To bring his mother back. His work has taken him to Congress, gotten him meetings with the likes of Donald Trump and Mark Zuckerberg, landed him on television. Along the way, he has grown into a steady force in the national immigration debate, a young but powerful voice for his family and the many others hoping to one day reunite.

•••

She was, by almost any standard, not a perfect mother. But she was his.

When Melba Soza left Jose and his twin brother, Jose Manuel, in Nicaragua and came to the U.S., the boys were just 3. Three years later when they were reunited, Jose had no memory of her. For years he called her "Melba," not mom.

She had created a new life in Miami. She lived with a boyfriend and soon was pregnant with a daughter. Jose, who came to the U.S. on a visa along with his brother, remembers those early years as happy ones.

But then Soza's boyfriend began drinking, money got tight, and they moved into a rat-infested trailer. Soon, Soza and her boyfriend began abusing the children, according to court papers. Child services officials were called to intervene, and Soza was ordered to participate in anger management classes.

Eventually, she left her boyfriend, who would win custody of their daughter. She rented a one-bedroom apartment for her and the boys, and got a job as a gas station cashier. And, says Jose, "she asked for forgiveness" for her sins of the past. "And I did forgive her," he says.

Then came his mother's arrest in September 2010 after a traffic stop. She might have been briefly detained and let go, but she had an outstanding warrant stemming from an earlier fight with the ex-boyfriend. And she was in the country illegally.

Prosecutors didn't pursue the criminal charges, but some six months later, Jose's mother was deported.

With their father, a man they barely knew, back in Nicaragua, Jose and his brother at first lived with an aunt. Jose's brother eventually moved in with his girlfriend's family, but Jose moved around -- staying with another aunt and then with a cousin in an apartment where he slept in a reclining chair covered in cigarette burns.

By then, Jose had missed a month of school and, at 17, could see his future slipping away. An immigration activist Jose had met shortly before his mother's arrest helped, getting his paperwork in order so that Jose could resume classes. The friend, Isabel Sousa-Rodriguez, also reached out to a lawyer when Jose decided to try foster care.

Sousa-Rodriguez also became the mentor Jose needed as he waded more deeply into the immigrant activist movement, his sights set on finding a way to get his mother back.

"I was so impressed by him," Sousa-Rodriguez says. "Being so young and so passionate about social justice. That's rare."

•••

At his foster home, Jose didn't act angry or depressed, just determined.

His foster mother, Jolie Bogorad, remembers him writing speeches and debating how the immigration system should be reformed. He started going to activist meetings, sometimes waking at 4 a.m. to attend weekend gatherings.

"I would say ... 'You don't want to sleep? Chill out? Have fun?,'" Bogorad recalls. "He'd say, 'After.'"

Within a year, Jose was a policy analyst for a state immigration network. He showed up at protests, leading chants and sharing his story. Last year, then a senior in high school, he led a group of activists inside U.S. Sen. Marco Rubio's Miami office, refusing to leave until they were granted a meeting with an aide.

He followed that with a letter to the editor of The Miami Herald, asking politicians to stand by a proposed bipartisan immigration reform measure, which included a provision to allow some deported immigrants with relatives still in the U.S. to return.

"I want my mom to be able to come back to Florida," Jose wrote, "and celebrate my graduation with me."

Instead, from afar, Soza saw snapshots of her son on Facebook, in his white cap and gown.

She moved from Nicaragua to Spain, and found a job caring for the elderly. Through Facebook, she watched his transformation from boy into man and activist, through the many pictures of him staging protests and meeting politicians.

They communicated through text messages and weekly phone calls. Sometimes Jose posted photographs on Facebook of her juxtaposed next to him, separate but together in one picture frame. "Dear Universe," he wrote in a post in May. "This is the last Mother's Day without my mom."

More than 100,000 parents of U.S. citizen children have been deported since 1998, according to U.S. Immigration and Customs Enforcement. The Applied Research Center, a New York-based advocacy organization, has found that at least 5,100 U.S. citizen children in 22 states are living in foster care because a parent has been detained or deported. An unknown number of non-citizen children have also been left behind.

While advocates such as Jose see immigration reform as the answer, others oppose the idea of allowing deported relatives to return, except in rare cases.

"Immigration law has no meaning if we deported people and then turn around and let them back in," says Jessica Vaughan, director of policy studies at the Center for Immigration Studies, which advocates tighter immigration policies.

Last year's Senate bill provided several potential avenues for deported relatives to return, including if they have a U.S. citizen or permanent resident child, spouse or parent in the country -- in Soza's case, her daughter. A policy forbidding deported immigrants from returning for 10 years also would have been lifted under the measure.

Though that bill stalled, President Barack Obama has once again called for Congress to take on immigration reform. House Republicans last week unveiled their broad strategy for overhauling the system, but some are already expressing skepticism about eventual passage.

Some immigration advocates fear stories such as Jose's could have opposite the intended effect. Several have cautioned him that his mother's previous actions could cast a bad light on all deported parents, jeopardizing other families' chances of being reunited. Others question how he could even want his mother back.

To Jose the answer is easy.

"I kind of need my mom," he says. "I should be able to hug her like everybody else."

A green card holder now, Jose is majoring in political science at Florida International University and will apply for citizenship as soon as legally allowed. Between classes, he continues his activism and works as a research associate for an organization that aims to engage politicians across the aisle on immigration reform. He has met with Republicans, Democrats -- even Donald Trump -- and talked at dozens of events.

At each gathering, he speaks of his mother.

Says U.S. Rep. Luis Gutierrez, D-Ill., an immigration reform supporter who met Jose through his work: "We should all be proud of this young man who has gone through so much, and yet continues to help others every day."

•••

Just before Christmas, Jose packed up his graduation pictures and placed some clothes in a duffel bag, along with a small American flag -- a gift for the mother he had not seen in nearly three years.

His friends raised the money for his ticket to Bilbao, Spain. There wasn't enough for a second fare for his brother, who, like Jose, obtained a green card and remains in Miami.

It was Christmas Day when Jose came down the terminal escalator to see his mother waiting in the arrival hall below. "Oh my son, my love," she said, wrapping him in an embrace as Jose began to cry.

"I was afraid you would have lost the love for your mother," she told him.

"I was afraid you'd look at me like a stranger," he said.

They had five days together, spent seeing the sites of Bilbao and taking in a movie and catching up on time missed. She told him she worried that she'd been a disappointment: "I feel ... like I have failed as a mother for being deported."

But Jose reassured her. "My mother has gone through a storm, but she doesn't lose sight of the sun," he said.

On their last day together, they awoke early and went the airport. Jose spoke about organizing an event to talk about his experience in Spain and seeing his mother after so long. He showed little emotion, until the time came to say goodbye once more.

With tears in his eyes, he hugged his mother. "Today I am stronger because of you."