Mark Keans, 39, is lying in a hospital bed in Brisbane.
The father-of-four, who has inoperable cancer in his brain and lungs, has been told he is unlikely to survive past Christmas.
But due to COVID-19 border closures, Keans' four children, who are currently in Sydney, have been unable to cross the border to see their dad.
Watch: Bruce Langborne speaks to The Today Show. Post continues below.
According to Bruce Langborne, the children's grandfather, the children "desperately want to see him".
"They told us we were being selfish – and we weren't taking into consideration the other patients," Langborne told 7News on Wednesday.
The Keans family have been told that only one of the man's four children, who are all aged under 13, can cross the border to visit him in hospital.
"I have no idea how you pick and choose which child goes," Mr Langborne told 7News.
"We’re bashing our heads against brick walls."
Speaking to The Today Show on Thursday morning, Langborne admitted that it has been a "hard" fight to get across the border.
"Well, basically, what [we were told by Queensland Health is], one, we had too many people trying to come up," he told The Today Show.
"Two, we weren't allowed to drive, we had to fly in and then we probably wouldn't get out of the airport anyway, they'd send us back," he continued.
"When you have a family choosing which child should say goodbye to their father, their dad, it's gone too far." Karl's heart-wrenching response to the Queensland family who have to choose which child gets to say goodbye to their dying father due to border restrictions. #9Today pic.twitter.com/EpelyiGJdk— The Today Show (@TheTodayShow) September 9, 2020