Ahmed Muthana, the father of two jihadists from Cardiff believed to have been fighting along with Reyaad Khan, fears that his sons are next on the UK government's 'hit list."
Nasser, 20 and Aseel, 17, are believed to be in Syria, alongside Khan who was killed by an RAF drone in Raqqa last month.
Muthana said: "I think they are on a hit list. They're targeting everyone now. I ask the prime minister not to target them but if they have evidence I don't mind, they deserve it ... but I don't think they are involved in attacks on the UK."
The 57-year-old retired electrical engineer who came to Britain from Yemen when he was 13 years old, said he was worried that it was only a matter of time before he received news that his boys have been killed in a targeted drone strike.
His son Nasser, a promising medical student, went to the same school as Khan and is thought to have become radicalised at about the same time. Nasser disappeared in November and later emerged on an Isis recruitment video together with Khan. Three months later, Aseel also disappeared and is believed to have joined the jihadists.
Earlier this year, Muthana expressed his devastation by what had happened but said that he had no choice but to disown his two sons for what they had done.
He however does not believe his children are involved in any plots against Britain. "They have made it clear they are not coming back. If they aren't coming back, how can they be involved in anything like that?" he asked, according to The Guardian.
"I know I won't see them again. I am sad they have gone," he said, adding that he did not have any contact with them.
The government has said that a list of names of several British jihadis was drawn up at the meeting of senior national security council members that approved the drone strike that killed both Ruhul Amin from Aberdeen and Khan.
Defence Secretary Michael Fallon has warned that the government was prepared to carry out further drone strikes against any British jihadist in Syria who were a threat to the UK.
Public should be given details of alleged plots against UK
Despite this, Muthana said the public deserved to know the details of what Khan had allegedly been plotting.
He told the Telegraph: "We have seen problems in the past with [former prime minister] Tony Blair and the Iraq war, so it is hard to know if what they are saying is true. I don't know if [Prime Minister] David Cameron is telling the truth. There have been problems with the intelligence in the past."
"In five years' time, we will be looking back and trying to find out what the truth is. I do not believe we will ever see the evidence."
Muthana told the BBC that he believes the UK wants to intervene in Syria and the prime minister is making excuses.
"He's making it up when he says there's information. If he has the proof then he has the right to kill them, but he should publish that proof. I think it was done for political reasons."