The mother of two brothers killed in the crash of Malaysia Airlines Flight 17 told CNN she regrets not taking her youngest son's fears about the flight more seriously.

Ten-year-old Miguel Calehr died alongside his older brother Shaka, 19, when the Malaysia Airlines jet came down in Ukraine, close to the border with Russia, last Thursday.

The pair were on their way to the Indonesian island of Bali for a fun-filled holiday with their grandmother.

Their middle brother, Mika, 16, was supposed to be on the flight too, but it was fully booked, and he had to take a seat on a later plane.

Just hours before the flight was to depart for Kuala Lumpur, Malaysia, Miguel told his mother he was nervous.

"After entering the passport [line], he came back to me and said 'Mama, I love you. I'm happy to see Oma [Grandma], but I'm going to miss you,'" Samira Calehr told CNN.

Then, she said, he asked her, "'What happens when the plane will crash?'

"I said, 'Come on, don't be silly, you've been traveling already so many times. Everything's going to be OK.'"

It was the sort of pre-flight fear many travelers will be familiar with, brushed off by a casual remark parents all over the world are used to making.

But single mom Calehr says she now wishes she'd paid more attention to his worries: "If I could just turn back time. I didn't listen to him. I don't know, I have no words to say..."

Still stunned by the tragedy which has overtaken her family, she pleads: "Why didn't they take my life? They are still young, they still have a future. Why? Why the children? Why not me?"

Samira's brother Harun told CNN his nephew Mika was being "very brave" - like his mother and grandmother.

"It comes in waves," he explained. "One minute they're completely distraught and inconsolable, and the other minute they're smiling and reminiscing and talking about the fun things that the boys did: the good things, the fun times, the memories."

Harun said the boys were good students. "They worked hard, they were honest, they were fun to be around." Above all, he said, "they were such a blessing to my sister. ... They were a joy to her, and the reason for her being."

The boys' grandmother, Yasmine Calehr, said the family was heartbroken: "Everybody is crying, everybody is losing something that belonged to them, but we feel like we have lost ourselves as well."

Harun said they were now focused on ensuring the boys' remains are repatriated to the Netherlands, where they can be given a proper farewell.

"As devastating as this process has been, we would like to have a grave, something to put into a grave... some remains or possibly the bodies intact to come home," he said.

Mika, now the only surviving son, told CNN he has lost his "best friends" but insists the bond he has with Miguel and Shaka will go on beyond the grave.

"It feels like they're already one with me now," he said. "They're my best friends, they're my brothers, and I feel like they're going to watch over me forever."