Parents of a child stuck in an orphanage in Pakistan have said they weep every night after having to leave him behind while they came to the UK.
Amin Rasheed and wife Anila Amin had to leave Ashar, seven, with his grandmother to get help for their seriously ill son Shahryar, five.
But after falling ill, she put him in an orphanage in December and now the family are desperate to get him a visa.
The Home Office said it "did not routinely comment on individual cases".
"There's not any night I could sleep without crying, without weeping for him, the same goes for his mother," said Mr Rasheed, who lives in Cardiff.
"Whenever we talk to him he cries a lot. He is unable to understand what is wrong, he says, 'why am I here? why am I not with you?', 'I don't want to live anymore,' and 'it's a very scary place."
The family, from Lahore, Pakistan, raised thousands of pounds to come to the UK in April 2019, after their youngest son, Shahryar, became seriously ill and doctors back home could not treat him.
When a visa application for the whole family was refused, the couple left their eldest child, Ashar, behind with his grandmother in the hope they would return in a matter of weeks.
But after finding out Shahryar had a life-threatening illness, which has left him paralysed from the neck down, they have been unable to go back home.
Ashar was placed in an orphanage after his grandmother got too ill to care for him.
Mr Rasheed said he was really worried his eldest son could have the same rare genetic condition, which can be triggered by the wrong diet.
"We are unable to sleep since the time he has been in the orphanage. It's really difficult to explain what exactly we are feeling," he said.
The family are now desperately trying to raise money to get Ashar to Cardiff so they can test him to check if he has the genetic condition.
His two-year-old sister Zoha has also been diagnosed with the condition, methylmalonic acidemia (MMA), which prevents people's bodies from processing certain fats and proteins, meaning they have to follow a strict diet.
Mr Rasheed said there was a 75% chance Ashar could also have the genetic disease, which can cause seizures, strokes or even a coma.
The family, who are living in Roath, believe Shahryar's illness was triggered by a stomach bug and said they had no choice but to come to the UK after he became a "skeleton".
They have spent all their savings, taken out loans and raised money to pay for his private hospital bills in Pakistan, and are facing a £74,000 bill for his treatment at Great Ormond Street Hospital.
Mr Rasheed said Shahryar's seizures were now under control and he had started to eat and even speak a few words.
But the family fear if they return to Pakistan, he will not get long-term medical care and they may be attacked or killed after getting threats due to the amount of money they borrowed to pay for his treatment.
They have applied for asylum, but human rights lawyer Chris Simmonds of Virgo Consultancy Service said it would cost at least £2,000 to get a visa to bring Ashar to the UK to be reunited with his family.
Cardiff Central MP Jo Stevens is planning to ask Home Secretary Priti Patel to ask for the visa fee to be waived and the family are trying to crowd fund the cash themselves.
"Time is of the essence and I would hope on a humanitarian basis that the Home Office and home secretary will think this is the right thing to do," she said.