Sebastian, who became ill in January of this year, has undergone brain surgery and chemotherapy after doctors discovered a tumour the size of a golfball at the back of his head.
Having complained of headaches and had to endure many mornings vomiting, Sebastian's concerned parents sought help, but struggled to find answers.
Speaking on RTÉ's Ray D' Arcy Show, Sebastian's father, Conor, said: "We were in and out of doctors and in and out of hospital a good few times. Sebastian was put on antibiotics and other medication, but no one knew what was wrong with him."
After noticing their son was developing a squint, Sebastian was brought to an optician who identified a build up of pressure behind the little boy's eye.
Having undergone an MRI scan in order to ascertain the cause of pressure, Sebastian and his family were dealt a devastating blow when they learned their little boy would require surgery to remove a tumour.
Hoping for the best, the family were yet again devastated to learn that while the main tumour had been removed, secondary tumours were identified.
Commenting on the aftermath of his son's surgery, Conor explained: "It took him weeks for him to come back around to himself."
Despite undergoing chemotherapy, the tumour has made a devastating reappearance, with Conor revealing a recent MRI scan was "pretty much as bad as it could be."
With incredibly poise, Conor revealed his son's prognosis, saying: "Originally they said he had months to live, but then on Monday we met with the team in Crumlin, the team that does radiation therapy, chemotherapy and the neurosurgeon, and the basically told us it's more like weeks."
Determined their son spends the last few weeks of his life creating a host of special memories, Sebastian's family want to bring Christmas forward and watch their little boy enjoy one of his favourite times of the year, saying: "Sebastian really loves Christmas like any child. He looks forward to it from one end of the year to the other."
In addition to requesting seasonal accessories, decorations and paraphernalia, Sebastian's family have revealed that their little boy is a massive fan of smash film Despicable Me, so are hoping they may be able to borrow some minion costumes for their early Christmas Day.
Paying tribute to members of the public for their considerable generosity thus far, Conor said: "We came home on Saturday and I found two Christmas trees sitting outside the front door. Real Christmas trees cut down that day, it was unbelievable."
Appealing to the public to get involved in Sebastian's special day, the Ray D'Arcy Show has asked people "to go out of their way a little bit and help to create a magical day for Sebastian."
Can you help create precious memories for this incredibly brave little boy?
If you wish to donate to Sebastian's cause, please contact ray@rte.ie
