Every two weeks, an 18-year-old in Texas buys lifesaving medication for his 11-year-old sister and sends it to Mexico.

He has been doing this for the past six months, since immigration authorities removed his five siblings from the United States — four of whom are U.S. citizens, including his then-10-year-old sister, who is recovering from a rare brain tumor. They were all sent to Mexico when authorities deported their parents, who lacked legal status.

The family’s absence has since weighed heavily on him as the oldest brother, who was left behind in the United States alone.

His once bustling home, where cookouts were hosted and life milestones were celebrated among family and friends, now feels empty, he said. Every time he steps into the house, a deep sense of loneliness overcomes him.

“There’s no one here. It’s just me,” he said, followed by a long pause. “It’s been pretty hard.”

The brother, who spoke exclusively to NBC News, is not being named out of concern for his family members’ safety after they were sent to an area of Mexico known for kidnappings of U.S. citizens.

He had been planning to go to college after finishing high school to pursue his dream career. Instead, he said, he’s working two jobs — one during the day at a fast-food restaurant and another at night at a gas station. The teen said he works so many hours a week that at times he barely gets to eat.

His family’s deportation has forced him to become their lifeline. When the loneliness and long work hours become overwhelming, he said, the ever-present memories of his young sister having seizures and being revived countless times at the hospital motivate him to keep going.

“At any moment, that brain tumor can come back, as her doctors said. That’s why she needs to keep getting the medicine that I buy,” said the 18-year-old, who is also a U.S. citizen.

His sister can’t access the medicine she needs from Mexico because the specialist doctors monitoring her recovery and prescribing her medicines are all in the U.S.

“It’s not cheap. At one point, it was like $300,” he said. “The insurance doesn’t cover it, so I’m paying for everything.”

After a deportation, hoping for parole

On Feb. 3, the family was driving from the Rio Grande Valley area, where they lived, to Houston, where the girl’s doctors are based, for an emergency medical checkup. On the way, they stopped at a stateside immigration checkpoint, one they have passed through multiple times. But this time, immigration authorities arrested the parents.

According to their attorney, Danny Woodward, they have never done anything to make them a priority for removal. The entire family was taken to a detention facility and sent to Mexico the following day.

The girl’s health condition has not improved since she’s been in Mexico, her mother told NBC News in June. Worsening headaches and dizziness have become so frequent that the girl’s parents take turns monitoring and taking care of her through the night.

The symptoms are indicative of some of the lasting side effects from the brain surgery that saved her life last year. Because the swelling in her brain is still not fully gone, the girl experiences difficulties with speech and mobility on the right side of her body, as well as memory problems. These require the girl to routinely check in with doctors monitoring her recovery, get MRI scans every three months, attend rehabilitation therapy sessions and take medication to prevent seizures.

But she has not been able to consistently access this care since the family was deported, her mother said.

The family applied for humanitarian parole with U.S. Citizenship and Immigration Services in June. They still have not heard back.

“It’s very, very stressful — just waiting for them to answer,” the girl’s brother said. “I don’t know why it’s taking so long.”

USCIS did not respond to a request for comment, but according to its website, applicants may demonstrate urgency by establishing a reason to be in the U.S. that calls for immediate action, including critical medical treatment or the need to visit, assist or support a relative who is ill.

A spokesperson for the Department of Homeland Security, which oversees USCIS, previously told NBC News that reports of the family’s situation are “inaccurate” and declined to speak on the specifics of the case, citing privacy reasons. The spokesperson said in a statement that when “someone is given expedited removal orders and chooses to disregard them, they will face the consequences.”

A church community calls for ‘compassion’ — and lends a hand

Marco Polo Coronado Jr., the lead pastor at the church the boy’s family began attending last year following his sister’s diagnosis, said allowing the family to come back so that their 11-year-old can receive the treatment she needs with the support of her entire family “seems like a no-brainer” to him.

“I don’t think it matters what political spectrum you come from. I think compassion is something that’s born from within us, that God puts there,” Coronado said. “When you find Jesus, when you have a relationship with Christ, it’s hard to avoid.”

“It is a wonderful family, and I think they go out of their way to try to make ends meet for their family and do all the right things for them and bring them up the right way,” Coronado said, adding that their “remarkable children” excel in music and the arts.

Keeping that hope alive, church volunteers showed up last month to help the boy fix up the house, so it’s in good shape when the family returns.

After a few days of work, everything “came out better than I expected,” the teen said.

With his family gone, the 18-year-old suddenly had bills to pay and a house to keep up. As he struggled to finish his last semester of senior year, he said he considered dropping out to work full time. But then he thought about his mother and the sacrifices she’s made, and that kept him in school.

He spent his 18th birthday and high school graduation without his family. He had thought that would be the time he’d be applying to colleges, the first step toward becoming a neurosurgeon — the same type of doctor who saved his sister’s life last year when she had her first brain surgery.

He recalled the moment he decided to pursue that career. It was the first time he met the neurosurgeon who operated on his sister. When the doctor came out of surgery, “his eyes went happy,” the teen recalled. “I was like, ‘That’s what I want to do.’” He’s put that on hold, indefinitely.